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Prosser, Robert James. "Robustness of multivariate mixed model ANOVA." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25511.
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In experimental or quasi-experimental studies in which a repeated measures design is used, it is common to obtain scores on several dependent variables on each measurement occasion. Multivariate mixed model (MMM) analysis of variance (Thomas, 1983) is a recently developed alternative to the MANOVA procedure (Bock, 1975; Timm, 1980) for testing multivariate hypotheses concerning effects of a repeated factor (called occasions in this study) and interaction between repeated and non-repeated factors (termed group-by-occasion interaction here). If a condition derived by Thomas (1983), multivariate multi-sample sphericity (MMS), regarding the equality and structure of orthonormalized population covariance matrices is satisfied (given multivariate normality and independence for distributions of subjects' scores), valid likelihood-ratio MMM tests of group-by-occasion interaction and occasions hypotheses are possible. To date, no information has been available concerning actual (empirical) levels of significance of such tests when the MMS condition is violated. This study was conducted to begin to provide such information.
Departure from the MMS condition can be classified into three types— termed departures of types A, B, and C respectively:
(A) the covariance matrix for population ℊ (ℊ = 1,...G), when orthonormalized, has an equal-diagonal-block form but the resulting matrix for population ℊ is unequal to the resulting matrix for population ℊ' (ℊ ≠ ℊ');
(B) the G populations' orthonormalized covariance matrices are equal, but the matrix common to the populations does not have equal-diagonal-block structure; or
(C) one or more populations has an orthonormalized covariance matrix which does not have equal-diagonal-block structure and two or more populations have unequal orthonormalized matrices.
In this study, Monte Carlo procedures were used to examine the effect of each type of violation in turn on the Type I error rates of multivariate mixed model tests of group-by-occasion interaction and occasions null hypotheses. For each form of violation, experiments modelling several levels of severity were simulated. In these experiments: (a) the number of measured variables was two; (b) the number of measurement occasions was three; (c) the number of populations sampled was two or three; (d) the ratio of average sample size to number of measured variables was six or 12; and (e) the sample size ratios were 1:1 and 1:2 when G was two, and 1:1:1 and 1:1:2 when G was three. In experiments modelling violations of types A and C, the effects of negative and positive sampling were studied.
When type A violations were modelled and samples were equal in size, actual Type I error rates did not differ significantly from nominal levels for tests of either hypothesis
except under the most severe level of violation. In type A experiments using unequal groups in which the largest sample was drawn from the population whose orthogonalized covariance matrix has the smallest determinant (negative sampling), actual Type I error rates were significantly higher than nominal rates for tests of both hypotheses and for all levels of violation. In contrast, empirical levels of significance were significantly lower than nominal rates in type A experiments in which the largest sample was drawn from the population whose orthonormalized covariance matrix had the largest determinant (positive sampling).
Tests of both hypotheses tended to be liberal in experiments which modelled type B violations. No strong relationships were observed between actual Type I error rates and any of: severity of violation, number of groups, ratio of average sample size to number of variables, and relative sizes of samples.
In equal-groups experiments modelling type C violations in which the orthonormalized
pooled covariance matrix departed at the more severe level from equal-diagonal-block form, actual Type I error rates for tests of both hypotheses tended to be liberal. Findings were more complex under the less severe level of structural departure. Empirical significance levels did not vary with the degree of interpopulation heterogeneity of orthonormalized covariance matrices.
In type C experiments modelling negative sampling, tests of both hypotheses
tended to be liberal. Degree of structural departure did not appear to influence actual Type I error rates but degree of interpopulation heterogeneity did. Actual Type I error rates in type C experiments modelling positive sampling were apparently related to the number of groups. When two populations were sampled, both tests tended to be conservative,
while for three groups, the results were more complex. In general, under all types of violation the ratio of average group size to number of variables did not greatly affect actual Type I error rates.
The report concludes with suggestions for practitioners considering use of the MMM procedure based upon the findings and recommends four avenues for future research on Type I error robustness of MMM analysis of variance. The matrix pool and computer programs used in the simulations are included in appendices.Education, Faculty of
Educational and Counselling Psychology, and Special Education (ECPS), Department of
Graduate
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Halldestam, Markus. "ANOVA - The Effect of Outliers." Thesis, Uppsala universitet, Statistiska institutionen, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-295864.
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This bachelor’s thesis focuses on the effect of outliers on the one-way analysis of variance and examines whether the estimate in ANOVA is robust and whether the actual test itself is robust from influence of extreme outliers. The robustness of the estimates is examined using the breakdown point while the robustness of the test is examined by simulating the hypothesis test under some extreme situations. This study finds evidence that the estimates in ANOVA are sensitive to outliers, i.e. that the procedure is not robust. Samples with a larger portion of extreme outliers have a higher type-I error probability than the expected level.
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Patrick, Joshua Daniel. "Simulations to analyze Type I error and power in the ANOVA F test and nonparametric alternatives." [Pensacola, Fla.] : University of West Florida, 2009. http://purl.fcla.edu/fcla/etd/WFE0000158.
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Lind, Ingela. "Regressor and Structure Selection : Uses of ANOVA in System Identification." Doctoral thesis, Linköping : Linköpings universitet, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-7000.
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An, Qian. "A Monte Carlo study of several alpha-adjustment procedures using a testing multiple hypotheses in factorial anova." Ohio : Ohio University, 2010. http://www.ohiolink.edu/etd/view.cgi?ohiou1269439475.
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Jordaan, Aletta Gertruida. "Empirical Bayes estimation of the extreme value index in an ANOVA setting." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86216.
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Thesis (MComm)-- Stellenbosch University, 2014.ENGLISH ABSTRACT: Extreme value theory (EVT) involves the development of statistical models and techniques in order to describe and model extreme events. In order to make inferences about extreme quantiles, it is necessary to estimate the extreme value index (EVI). Numerous estimators of the EVI exist in the literature. However, these estimators are only applicable in the single sample setting. The aim of this study is to obtain an improved estimator of the EVI that is applicable to an ANOVA setting. An ANOVA setting lends itself naturally to empirical Bayes (EB) estimators, which are the main estimators under consideration in this study. EB estimators have not received much attention in the literature. The study begins with a literature study, covering the areas of application of EVT, Bayesian theory and EB theory. Different estimation methods of the EVI are discussed, focusing also on possible methods of determining the optimal threshold. Specifically, two adaptive methods of threshold selection are considered. A simulation study is carried out to compare the performance of different estimation methods, applied only in the single sample setting. First order and second order estimation methods are considered. In the case of second order estimation, possible methods of estimating the second order parameter are also explored. With regards to obtaining an estimator that is applicable to an ANOVA setting, a first order EB estimator and a second order EB estimator of the EVI are derived. A case study of five insurance claims portfolios is used to examine whether the two EB estimators improve the accuracy of estimating the EVI, when compared to viewing the portfolios in isolation. The results showed that the first order EB estimator performed better than the Hill estimator. However, the second order EB estimator did not perform better than the “benchmark” second order estimator, namely fitting the perturbed Pareto distribution to all observations above a pre-determined threshold by means of maximum likelihood estimation.
AFRIKAANSE OPSOMMING: Ekstreemwaardeteorie (EWT) behels die ontwikkeling van statistiese modelle en tegnieke wat gebruik word om ekstreme gebeurtenisse te beskryf en te modelleer. Ten einde inferensies aangaande ekstreem kwantiele te maak, is dit nodig om die ekstreem waarde indeks (EWI) te beraam. Daar bestaan talle beramers van die EWI in die literatuur. Hierdie beramers is egter slegs van toepassing in die enkele steekproef geval. Die doel van hierdie studie is om ’n meer akkurate beramer van die EWI te verkry wat van toepassing is in ’n ANOVA opset. ’n ANOVA opset leen homself tot die gebruik van empiriese Bayes (EB) beramers, wat die fokus van hierdie studie sal wees. Hierdie beramers is nog nie in literatuur ondersoek nie. Die studie begin met ’n literatuurstudie, wat die areas van toepassing vir EWT, Bayes teorie en EB teorie insluit. Verskillende metodes van EWI beraming word bespreek, insluitend ’n bespreking oor hoe die optimale drempel bepaal kan word. Spesifiek word twee aanpasbare metodes van drempelseleksie beskou. ’n Simulasiestudie is uitgevoer om die akkuraatheid van beraming van verskillende beramingsmetodes te vergelyk, in die enkele steekproef geval. Eerste orde en tweede orde beramingsmetodes word beskou. In die geval van tweede orde beraming, word moontlike beramingsmetodes van die tweede orde parameter ook ondersoek. ’n Eerste orde en ’n tweede orde EB beramer van die EWI is afgelei met die doel om ’n beramer te kry wat van toepassing is vir die ANAVA opset. ’n Gevallestudie van vyf versekeringsportefeuljes word gebruik om ondersoek in te stel of die twee EB beramers die akkuraatheid van beraming van die EWI verbeter, in vergelyking met die EWI beramers wat verkry word deur die portefeuljes afsonderlik te ontleed. Die resultate toon dat die eerste orde EB beramer beter gevaar het as die Hill beramer. Die tweede orde EB beramer het egter slegter gevaar as die tweede orde beramer wat gebruik is as maatstaf, naamlik die passing van die gesteurde Pareto verdeling (PPD) aan alle waarnemings bo ’n gegewe drempel, met behulp van maksimum aanneemlikheidsberaming.
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Zhang, Bairu. "Functional data analysis in orthogonal designs with applications to gait patterns." Thesis, Queen Mary, University of London, 2018. http://qmro.qmul.ac.uk/xmlui/handle/123456789/44698.
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This thesis presents a contribution to the active research area of functional data analysis (FDA) and is concerned with the analysis of data from complex experimental designs in which the responses are curves. High resolution, closely correlated data sets are encountered in many research fields, but current statistical methodologies often analyse simplistic summary measures and therefore limit the completeness and accuracy of conclusions drawn. Specifically the nature of the curves and experimental design are not taken into account. Mathematically, such curves can be modelled either as sample paths of a stochastic process or as random elements in a Hilbert space. Despite this more complex type of response, the structure of experiments which yield functional data is often the same as in classical experimentation. Thus, classical experimental design principles and results can be adapted to the FDA setting. More specifically, we are interested in the functional analysis of variance (ANOVA) of experiments which use orthogonal designs. Most of the existing functional ANOVA approaches consider only completely randomised designs. However, we are interested in more complex experimental arrangements such as, for example, split-plot and row-column designs. Similar to univariate responses, such complex designs imply that the response curves for different observational units are correlated. We use the design to derive a functional mixed-effects model and adapt the classical projection approach in order to derive the functional ANOVA. As a main result, we derive new functional F tests for hypotheses about treatment effects in the appropriate strata of the design. The approximate null distribution of these tests is derived by applying the Karhunen- Lo`eve expansion to the covariance functions in the relevant strata. These results extend existing work on functional F tests for completely randomised designs. The methodology developed in the thesis has wide applicability. In particular, we consider novel applications of functional F tests to gait analysis. Results are presented for two empirical studies. In the first study, gait data of patients with cerebral palsy were collected during barefoot walking and walking with ankle-foot orthoses. The effects of ankle-foot orthoses are assessed by functional F tests and compared with pointwise F tests and the traditional univariate repeated-measurements ANOVA. The second study is a designed experiment in which a split-plot design was used to collect gait data from healthy subjects. This is commonly done in gait research in order to better understand, for example, the effects of orthoses while avoiding confounded analysis from the high variability observed in abnormal gait. Moreover, from a technical point of view the study may be regarded as a real-world alternative to simulation studies. By using healthy individuals it is possible to collect data which are in better agreement with the underlying model assumptions. The penultimate chapter of the thesis presents a qualitative study with clinical experts to investigate the utility of gait analysis for the management of cerebral palsy. We explore potential pathways by which the statistical analyses in the thesis might influence patient outcomes. The thesis has six chapters. After describing motivation and introduction in Chapter 1, mathematical representations of functional data are presented in Chapter 2. Chapter 3 considers orthogonal designs in the context of functional data analysis. New functional F tests for complex designs are derived in Chapter 4 and applied in two gait studies. Chapter 5 is devoted to a qualitative study. The thesis concludes with a discussion which details the extent to which the research question has been addressed, the limitations of the work and the degree to which it has been answered.
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Gonsalez, Camila Gianini [UNESP]. "Metodologias para reconhecimento de padrões em sistemas SHM utilizando a técnica da Impedância Eletromecânica (E/M)." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/94506.
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gonsalez_cg_me_ilha.pdf: 4679748 bytes, checksum: 5f6a627734b2110f92059053c2470814 (MD5)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Pesquisadores de diversas partes do mundo se empenham em desenvolver técnicas capazes de monitorar a integridade de máquinas, veículos e estruturas, principalmente as que a ruptura ou destruição possa provocar acidentes e catástrofes. Neste contexto, várias técnicas não destrutivas podem ser utilizadas para monitorar estes sistemas permitindo a realização de reparos e, evitando maiores prejuízos econômicos e danos sociais. A técnica da Impedância Eletromecânica está entre as técnicas baseadas na utilização de materiais piezelétricos e, particularmente, utiliza-se de uma curva sensível a pequenas variações na estrutura, característica que faz a técnica ser eficiente na detecção de danos incipientes. No entanto, sob variações das condições ambiente e de teste, a sensibilidade da técnica pode produzir falsos diagnósticos. Desta forma, o desafio atual é aplicar a técnica da Impedância Eletromecânica em sistemas de monitoramento considerando condições mais próximas às condições de operação reais dos sistemas a serem monitorados. Este trabalho apresenta duas metodologias para sistemas SHM, a primeira consiste em utilizar a técnica de agrupamento Fuzzy c-means para entender e considerar o efeito da temperatura nos sinais da Impedância Eletromecânica. A segunda metodologia utiliza análise de variância (ANOVA) para propor uma metodologia de detecção mais robusta, e assim, incorporar variações aleatórias nos sistemas de medição e aquisição sem comprometer o diagnóstico SHM
Researchers around the world are engaged to develop techniques for structural health monitoring of machinery, vehicles and structures, especially systems where damage or destruction could induce accidents and disasters. In this context, several non-destructive techniques can be used to monitor these systems allowing repairs and avoiding major economic losses or social losses. The electromechanical impedance technique is among the techniques based on piezoelectric materials use and it is sensible to small variations in the structure which makes it efficient in detecting incipient damages. However, variations in the ambient or test conditions can cause false diagnoses. Therefore, the current challenge is to apply the electromechanical impedance technique considering monitoring conditions closer to real operating conditions of the systems to be monitored. This work presents two methodologies for SHM systems. The first one uses Fuzzy c-means clustering to distinguish the temperature effect on impedance signal. The second method uses analysis of variance (ANOVA) to propose a more robust detection methodology and thus incorporate random variations in measurement systems and acquisition without loss of SHM diagnostic
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Gonsalez, Camila Gianini. "Metodologias para reconhecimento de padrões em sistemas SHM utilizando a técnica da Impedância Eletromecânica (E/M) /." Ilha Solteira : [s.n.], 2012. http://hdl.handle.net/11449/94506.
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Orientador: Vicente Lopes JuniorBanca: Samuel Silva
Banca: Michael John Brennan
Banca: Carlos Alberto Cimini Junior
Resumo: Pesquisadores de diversas partes do mundo se empenham em desenvolver técnicas capazes de monitorar a integridade de máquinas, veículos e estruturas, principalmente as que a ruptura ou destruição possa provocar acidentes e catástrofes. Neste contexto, várias técnicas não destrutivas podem ser utilizadas para monitorar estes sistemas permitindo a realização de reparos e, evitando maiores prejuízos econômicos e danos sociais. A técnica da Impedância Eletromecânica está entre as técnicas baseadas na utilização de materiais piezelétricos e, particularmente, utiliza-se de uma curva sensível a pequenas variações na estrutura, característica que faz a técnica ser eficiente na detecção de danos incipientes. No entanto, sob variações das condições ambiente e de teste, a sensibilidade da técnica pode produzir falsos diagnósticos. Desta forma, o desafio atual é aplicar a técnica da Impedância Eletromecânica em sistemas de monitoramento considerando condições mais próximas às condições de operação reais dos sistemas a serem monitorados. Este trabalho apresenta duas metodologias para sistemas SHM, a primeira consiste em utilizar a técnica de agrupamento Fuzzy c-means para entender e considerar o efeito da temperatura nos sinais da Impedância Eletromecânica. A segunda metodologia utiliza análise de variância (ANOVA) para propor uma metodologia de detecção mais robusta, e assim, incorporar variações aleatórias nos sistemas de medição e aquisição sem comprometer o diagnóstico SHM
Abstract: Researchers around the world are engaged to develop techniques for structural health monitoring of machinery, vehicles and structures, especially systems where damage or destruction could induce accidents and disasters. In this context, several non-destructive techniques can be used to monitor these systems allowing repairs and avoiding major economic losses or social losses. The electromechanical impedance technique is among the techniques based on piezoelectric materials use and it is sensible to small variations in the structure which makes it efficient in detecting incipient damages. However, variations in the ambient or test conditions can cause false diagnoses. Therefore, the current challenge is to apply the electromechanical impedance technique considering monitoring conditions closer to real operating conditions of the systems to be monitored. This work presents two methodologies for SHM systems. The first one uses Fuzzy c-means clustering to distinguish the temperature effect on impedance signal. The second method uses analysis of variance (ANOVA) to propose a more robust detection methodology and thus incorporate random variations in measurement systems and acquisition without loss of SHM diagnostic
Mestre
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Joubert, Ronel. "Factors influencing the degree of burnout experienced by nurses working in neonatal intensive care units." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20217.
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Thesis (MCur)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Burnout is one of the challenges that nurses are faced with in their stressful and rapidly changing work environment. The vulnerability of nurses to burnout remains a major concern which affects both the individual and institution. Knowledge about burnout and associated risk factors which influence the development of burnout is vital for early recognition and intervention. The research question which guided this study was: “What are the factors influencing the degree of burnout experienced by nurses working in neonatal intensive care units?” The objectives included determining which physical, psychological, social and occupational factors influenced the degree of burnout experienced by nurses. A descriptive, explorative research design with a quantitative approach was applied. The target population consisted of (n=105) permanent nursing staff members working in the neonatal units of two different hospitals. A convenience sampling method was used. Participants (n=102) who gave voluntary consent to participate was included in the study. Validity and reliability was supported through the use of a validated questionnaire, Maslach Burnout Inventory – General Survey including a section based on demographical information and a section based on physical, psychosocial, social and occupational factors. Validity of the questionnaire was supported by the use of a research methodologist, nurse expert and a statistician in the particular field. A pilot study was done to test the feasibility of the study and to test the questionnaire for any errors and ambiguities. Ethics approval was obtained from Stellenbosch University and permission from the Heads of the hospitals where the study was conducted. The data was analyzed with the assistance of a statistician and these are presented in histograms, tables and frequencies. The relationship between response variables and nominal input variables was analysed using analysis of variance (ANOVA). Various statistical tests were applied to determine statistical associations between variables such as the Spearman test, using a 95% confidence interval. Results have shown that participants experienced an average level of emotional exhaustion, a high level of professional efficacy and a low level of cynicism. Further analyses have shown that there is a statistical significant difference between emotional exhaustion and the rank of the participant (p=<0.01), highest qualification (p=0.05) and a high workload (p=0.01). Furthermore a statistical significant difference was found between professional efficacy and rank of participants (p=<0.01). In addition a statistical significant difference was found between cynicism and the number of years participants were in the profession (p=0.05). Multiple factors were determined in this study that influences the degree of burnout nurses experience. The majority of participants (n=56/55%) experienced decreased job satisfaction and accomplishment, (n=52/51%) of participants experienced that their workload is too much for them and (n=63/62%) participants received no recognition for their work. Recommendations are based on preventative measures, because preventing burnout is easier and more cost-effective than resolving burnout once it has occurred. In conclusion, the prevention strategies, early recognition of work stress and appropriate interventions are crucial in addressing the problem of burnout.
AFRIKAANSE OPSOMMING: Uitbranding is een van die uitdagings waarmee verpleegsters te kampe het in hulle stresvolle en vinnig veranderende werkomgewing. Die kwesbaarheid van verpleegsters vir uitbranding bly ’n kritieke bekommernis wat beide die individu en die inrigting affekteer. Kennis omtrent uitbranding en verwante risiko faktore wat die ontwikkeling van uitbranding beïnvloed, is deurslaggewend vir vroeë opsporing en intervensie. Die navorsingsvraag wat hierdie studie gelei het, is: “Wat is die faktore wat die mate van uitbranding beïnvloed wat deur verpleegsters ondervind word wat in neonatale intensiewe sorgeenhede werk?” Die doelwitte wat ingesluit is, is om te bepaal watter fisiese, sielkundige, maatskaplike en beroepsfaktore die mate van uitbranding wat deur verpleegsters ervaar word, beïnvloed. ’n Beskrywende, ondersoekende navorsingsontwerp met ’n kwantitatiewe benadering is toegepas. Die teikengroep het bestaan uit (n=105) permanente verpleegpersoneel wat in die neonatale eenhede van twee verskillende hospitale werk. ’n Gerieflikheidsteekproef metode is gebruik. Deelnemers (n=102) wat vrywillige toestemming gegee het om deel te neem, is ingesluit in die navorsingstudie. Geldigheid en betroubaarheid is ondersteun deur die gebruik van ’n geldige vraelys van “Maslach Burnout Inventory – General Survey”, asook ’n afdeling gebaseer op demografiese inligting en ’n afdeling gebaseer op fisiese, sielkundige, maatskaplike en beroepsfaktore. Geldigheid van die vraelys is ondersteun deur ’n navorsingsmetodoloog, ’n verpleegspesialis en ’n statistikus op die navorsingsgebied. ’n Loodsondersoek is gedoen om die haalbaarheid van die studie te toets en om die vraelys te toets vir enige foute en dubbelsinnighede. Etiese goedkeuring is verkry van die Universiteit van Stellenbosch en goedkeuring van die Hoofde van die hospitale waar die studie uitgevoer is. Die data is geanaliseer met die hulp van ’n statistikus en is aangebied in histogramtafels en frekwensies. Die verwantskap tussen responsveranderlikes en nominale insetveranderlikes is geanaliseer deur gebruik te maak van die analise van variansie (ANOVA). Verskeie statistiese toetse is toegepas om statistiese assosiasies tussen veranderlikes te bepaal, soos deur van die Spearmantoets gebruik te maak, met ’n 95% betroubaarheidsinterval. Resultate het bewys dat deelnemers ’n gemiddelde vlak van emosionele uitputting, ’n hoë vlak van professionele effektiwiteit en ’n lae vlak van sinisme ervaar. Verdere analise het bewys dat daar ’n statistiese beduidende verskil tussen emosionele uitputting en die rang van die deelnemers (p=<0.01) is, hoogste kwalifikasie (p=0.05) en ’n hoë werklading (p=0.01). Verder is ’n statistiese beduidende verskil gevind tussen professionele effektiwiteit en rang van deelnemers (p=<0.01). Saam hiermee is ’n statistiese beduidende verskil gevind tussen siniesheid en die aantal jare wat deelnemers in die beroep is (p=0.05). Voorts, is veelvuldige faktore bepaal in hierdie studie wat die mate van uitbranding beïnvloed wat verpleegsters ervaar. Die meeste van die deelnemers (n=56/55%) het ’n afname in werksbevrediging en -verrigting ervaar, (n=52/51%) deelnemers het ervaar dat hul werklading te veel is vir hulle en (n=63/62%) deelnemers het geen erkenning vir hulle werk ontvang nie. Aanbevelings is gebaseer op voorkomende maatreëls, want om uitbranding te voorkom, is makliker en meer koste-effektief as om uitbranding te probeer oplos as dit alreeds begin het. Ten slotte, die voorkomende strategieë, vroeë identifisering van werkstres en geskikte intervensies is deurslaggewend om die probleem van uitbranding aan te spreek.
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Höög, Andrée, and Christoffer Wrangenby. "Studenters förhållning till Javas kodkonventioner inom högskoleingenjörsutbildningar i Sverige - En komparativ studie." Thesis, Malmö högskola, Fakulteten för teknik och samhälle (TS), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-20454.
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Att sätta sig in i andra utvecklares kod kan vara svårt och tidskrävande. Kodkonventionerär framtagna i syfte att underlätta underhållsarbetet för andra utvecklare som arbetar medsamma projekt, då det sällan är personen som skrev programmet som sedan underhållersamma program. För lite fokus läggs på kvalitétsaspekten i utvecklingsfasen av projektvilket kostar företag pengar och resurser. Denna studie har för avsikt att undersöka hurhögskoleingenjörsstudenter inom datateknik vid olika lärosäten i Sverige förhåller sig tillJavas kodkonventioner, och om det går att urskilja en signifikant skillnad i kodkvalitémellan lärosäten i avseende på identifierare, kommentarer samt format och struktur. Enwebbenkätundersökning genomfördes vars empiri analyserades med hjälp av ANOVA somär en vedertagen metod för hypotesprövning. 21 av 23 ANOVA-test visade att ingen signifikantskillnad förekom mellan lärosätena i avseende på identifierare, kommentarer samtformat och struktur. Resultatet visade även att de kvalitétsaspekter studenterna tyckerär viktiga och prioriterar att lägga tid på är också de aspekter som studenterna tycks hastörst förståelse och kunskap kring.To get acquainted with other developers code can be difficult and time consuming. Codeconventions are developed in order to facilitate maintenance work for other developersworking on the same project, where the person who wrote the program rarely is the personthat maintains the same program. Little attention is paid to the aspect of quality ina projects development phase, which costs companies money and resources. This studyintends to investigate how students studying for a Bachelor of Science in Engineering inComputer Science at various universities in Sweden relate to Java code conventions, andif it is possible to discern a significant difference in code quality between these universitiesin terms of identifiers, comments, format and structure. An online survey was conductedwhose empirical data was analyzed using ANOVA, which is a recognized method forstatistical hypothesis testing. 21 of 23 ANOVA test showed that no significant differenceexisted between the institutions in terms of identifiers, comments and format and structure.The results also showed that the aspects of quality, which the students think are themost important, are also in fact the aspects they have the greatest understanding andknowledge about.
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Varanda, Luciano Donizeti. "Produção e avaliação do desempenho de painéis de partículas de Eucalyptus grandis confeccionados com adição de casca de aveia." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-09082012-165028/.
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Os painéis à base de madeira vêm sendo amplamente utilizados em todo o mundo, em resposta à redução de oferta de madeira maciça em diversos segmentos da indústria madeireira, como em móveis, painéis, estruturas e outros componentes na construção civil. O grande volume de resíduos gerados pela agroindústria viabiliza o desenvolvimento de materiais alternativos e sustentáveis, destacando-se os painéis de partículas. Este trabalho apresenta um estudo da produção e avaliação de painéis de partículas de Eucalyptus grandis e casca de aveia, aderidas sob pressão com dois tipos de resinas (poliuretana à base de mamona e ureia formaldeído). O desempenho físico-mecânico dos painéis produzidos foi avaliado com base na ABNT NBR 14810:2006. Por meio de análise de variância (ANOVA), avaliou-se a influência dos fatores adotados: madeira de Eucalyptus grandis, com proporções mássicas de 70, 85 e 100%; casca de aveia, nas proporções de 15, 30 e 100%; e adesivos, nas proporções de 10, 12 e 14%, bem como a combinação entre ambos, em cada uma das variáveis respostas (propriedades físico-mecânicas) avaliadas. Os resultados apontaram excelentes propriedades físico-mecânicas, em alguns casos muito superiores aos requisitos estipulados pelas normas nacionais e internacionais. Desta maneira, ficou comprovado o bom desempenho dos painéis de partículas produzidos, além de sua compatibilidade para aplicações em indústrias, como de móveis, painéis, embalagens e na construção civil.Wood-based panels have been widely used around the world, replacing solid wood in various segments of the industry, such as furniture, panels, structures and other building components. The large volume of waste generated by agro industry enables the development of alternative and sustainable materials, highlighting the particleboard. This paper presents a study about production and evaluation of particleboard of Eucalyptus grandis and oat hulls, bonded under pressure with two types of resins (polyurethane based on castor oil and urea formaldehyde). Physical-mechanical performance of the panels produced was evaluated based on ABNT NBR 14810:2006. A variance analysis (ANOVA) evaluated the factors influence: Eucalyptus grandis, with mass ratios of 70, 85 and 100%; oat hulls, in proportions of 15, 30 and 100%; adhesives, in proportions of 10, 12 and 14%, and the combination of both, in each of the response variables (physical and mechanical properties) evaluated. Results showed excellent physical-mechanical properties, in some cases much higher than national and international codes requirements. Thus, panel particles good performance was proved, in addition to its compatibility with applications in wood industries, such as furniture, panels, packaging and in building construction.
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Copeland, Matthew Blair. "Learner Modal Preference and Content Delivery Method Predicting Learner Performance and Satisfaction." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc862858/.
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The purpose of the study was to investigate how the online, computer-based learner's personal learning profile (Preference), the content delivery method supplemented with visual content based on Neil Fleming's VARK (visual, aural, read/write, kinesthetic) model (Content), and the interaction of Preference and Content, influenced learner performance (Performance) and/or learner self-reported satisfaction (Satisfaction). Participants were drawn from a population of undergraduates enrolled in a large public southwestern research university during the fall 2015 semester. The 165 student participants (13.79% completion rate) were comprised of 52 (31.5%) females and 113 (68.5%) males age 18-58+ years with 126 (76.4%) age 18-24 years. For race/ethnicity, participants self-identified as 1 (0.66%) American Indian/Alaska Native, 21 (12.7%) Asian/Pacific Islander, 27 (16.4%) Black, non-Hispanic, 28 (17%) Hispanic, 78 (47.3%) White, non-Hispanic, 10 (6.1%) other. Reported socioeconomic status was 22 (13.3%) withheld, 53 (32.1%) did not know, 45 (27.3%) low, 13 (7.9%) moderately low, 16 (9.7%) middle, 8 (4.8%) upper middle, and 8 (4.8%) upper.
This causal-comparative and quasi-experimental, mixed-method, longitudinal study used researcher-developed web-based modules to measure Performance and Satisfaction, and used the criterion p < .05 for statistical significance. A two-way, 4 x 3 repeated measures (Time) analysis of variance (RM-ANOVA) using Preference and Content was statistically significant on each Performance measure over Time, and at two measures on Satisfaction over Time. The RM-ANOVA was statistically significant on between-subjects main effect Performance for read/write modality Content compared to aural and kinesthetic Content. There were no statistically significant main effects observed for Satisfaction. A Pearson r correlation analysis showed that participants that were older, married, and of higher socioeconomic status performed better. The correlation analysis also showed that participants who performed better reported greater likelihood to take online courses in the future, higher motivation, sufficient time and support for studies, and sufficient funding for and access to the Internet.
The study results suggested that regardless of Preference, using read/write modality Content based on the VARK model while maintaining the verbal language can yield better Performance outcomes. The study results also suggested that while maintaining the verbal language, Preference, and Content based on the VARK model do not distinguish learner Satisfaction outcomes. However, because Satisfaction has been shown to impact Performance, efficacy, and retention, it matters to educational institutions. Future research should consider more granular models and factorial research methods, because models that utilize a single representative construct score can mask effects when analyzing Performance and Satisfaction.
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Varanda, Luciano Donizeti. "Painéis de alta densidade para aplicação em pisos: produção e avaliação de desempenho." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-16112016-174123/.
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Temas relacionados ao desenvolvimento de novos materiais têm sido cada vez mais abordados e discutidos, num contexto em que questões como meio ambiente, sociedade, economia de energia e aproveitamento de resíduos, vêm se tornando relevantes. Neste cenário, faz-se necessário estudar aplicações de insumos alternativos na produção de pisos de madeira, tanto para reduzir o consumo de essências tropicais quanto para suprir o aumento da demanda de madeira nas indústrias deste segmento. O objetivo deste estudo foi produzir painéis de partículas homogêneos de alta densidade, com resíduos de madeira de Pinus elliottii e casca de aveia (Avena sativa), aderidos sob pressão com dois tipos de adesivo, poliuretano à base de óleo de mamona e melamina formaldeído, nos percentuais de 11 e 13%, e avaliar o desempenho físico-mecânico de tais painéis para aplicação em pisos. O desempenho físico-mecânico dos painéis (Planejamento I - 20 tratamentos) foi avaliado com base nas normas ABNT NBR 14810 (2006 e 2013). Realizou-se análise de variância (ANOVA) para testar a influência dos fatores individuais (percentual de casca de aveia, percentual de adesivo e tipo de adesivo), além das interações entre tais fatores (dois a dois e três a três) nas propriedades físico-mecânicas dos painéis. Também foi avaliado o desempenho para pisos, tanto dos painéis (Planejamento II - 12 tratamentos) quanto de três espécies de madeira tropical (Angelim Vermelho, Dinizia excelsa; Cumaru, Dipteryx odorata e Jatobá, Hymenaea sp.), segundo diversas normas relacionadas a pisos de madeira. Os resultados apontaram propriedades físico-mecânicas dos painéis, em alguns tratamentos superiores aos requisitos estipulados por normas nacionais e internacionais. Quanto ao desempenho para pisos, os painéis apresentaram desempenho semelhante as três espécies de madeira, na maioria das propriedades avaliadas. A análise de porosimetria por intrusão de mercúrio confirmou a similaridade entre os painéis (do Planejamento II) e as três espécies de madeira avaliadas, evidenciando a potencialidade dos painéis produzidos para aplicação na indústria de pisos engenheirados.Matters related to the development of new materials have been increasingly addressed and discussed in a context where issues such as the environment, society, energy and waste recovery economy, is becoming relevant. In this scenario, it is necessary to study alternative inputs for applications in the production of wood floors, both to reduce the consumption of tropical essences as to meet the increasing demand for wood in industries in this segment. The aim this study was to produce high density homogeneous particleboard with waste wood of Pinus elliottii and oat hulls (Avena sativa), adhered under pressure with two types of adhesive, castor oil-based polyurethane and melamine formaldehyde, the percentage of 11 and 13%, and evaluate the physical and mechanical performance of such panels for use in floors. The physical-mechanical performance of the panels (Planning I - 20 treatments) was evaluated based on the NBR 14810 (2006 and 2013) standards. We conducted an analysis of variance (ANOVA) to evaluate the influence of individual factors (oat hulls percentage, adhesive percentage and type of adhesive), and the interactions between these factors (two by two and three by three) on the physical properties-mechanical panels. It was also evaluated the performance for floors, both panels (Planning II - 12 treatments) as three species of tropical wood (Angelim Vermelho, Dinizia excelsa; Cumaru, Dipteryx odorata e Jatobá, Hymenaea sp.), according to various standards related to wood floors. The results indicated physical and mechanical properties of the panels, in some treatments superior to the requirements stipulated by national and international standards. As for performance flooring, panels statistically equivalent to the three species of wood, most of the evaluated properties. Porosimetry analysis by mercury intrusion confirmed the similarity between the panels (from Planning II) and the three wood species evaluated, demonstrating the potential of the panels produced for use in the flooring industry engineered.
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Mankayi, Dolphia Thozama. "An investigation into the relationship between satisfaction with life and sense of coherence amongst the unemployed." University of the Western Cape, 1996. http://hdl.handle.net/11394/7861.
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Magister Commercii (Industrial Psychology) - MCom(IPS)The present study investigated the relationship between the Sense Of Coherence and Satisfaction With Life amongst the unemployed. The study attempted to test the following hypotheses. 1. People with a high Sense Of Coherence tend to be satisfied with their lives in general. 2. Demographic variables such as age, gender, race and level of education have an influence on the subjects' scores on the Sense Of Coherence and Satisfaction With Life scales. 3. Length of unemployment has an impact on the subjects' Sense Of Coherence and Satisfaction With Life. In this study, subjects were drawn from the Department of Manpower in the Western Cape region. The data were obtained from a sample of 100 participants. Of this 100, 52 were males. Subjects were asked to complete the Sense Of Coherence and the Satisfaction With Life scales. Statistical procedures that were used are Multiple Linear Regression analysis, Product Moment Correlational Co-efficients, Analysis of Variance test (ANOVA) and the Cronbach Alphas of the various scales. It was found that Sense Of Coherence correlated significantly with Satisfaction With Life, thus supporting the first hypothesis. This led to the conclusion that a person with a strong Sense Of Coherence tends to be more satisfied with his/her life. However, a person with a weaker Sense Of Coherence finds it difficult to make sense out of his/her life. It was also found that most of the demographic variables did not reach any statistical significance. The general trend in this sample was that younger people had higher education and had been unemployed for fewer years. In comparison, older people were found to have less education and had been unemployed for more years. It was concluded that formal and informal education system will be necessary to develop and equip both young and older people with the experience and skills to use at work. This study was concluded by the discussion of the implications of the findings and suggestions for future research.
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Souza, Amós Magalhães de. "Produção e avaliação do desempenho de compósitos à base de madeira a partir de insumos alternativos." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-27112017-102235/.
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A utilização de produtos provenientes de fontes renováveis e livres de substâncias tóxicas é tendência global, prova disso é o constante aumento da demanda por produtos à base de madeira. Segundo o Forest Products Statistics (2015), a produção mundial de painéis de madeira reconstituída, em 2014, foi de 388 milhões de m³, um aumento de 5,5% em comparação com o ano anterior e um aumento de 34% quando comparado com 2010. No entanto, o setor industrial de painéis de madeira há décadas enfrenta um grande desafio com relação às emissões tóxicas vindas dos adesivos convencionais. Diante destes problemas, a proposta do presente trabalho foi testar a viabilidade da produção de painéis aglomerados e painéis OSB, com significativa redução da emissão de formaldeído, a partir de resíduos de madeira de Pinus sp. e Tectona grandis (Teca). Neste sentido, buscou-se contribuir para o aumento do conhecimento científico sobre a utilização do polímero natural polihidroxibutirato (PHB) e do resíduo de tinta à base de resina epóxi como adesivos alternativos. Os painéis foram fabricados variando-se os parâmetros de produção para obtenção de melhores condições de processo, sendo estes: densidade baixa, média e alta; teor de adesivo de 20, 30 e 40%; adição de partículas de Teca nas proporções de 0, 25, 50, 75, 100%. O desempenho físico-mecânico dos painéis foi avaliado com base nas normas ABNT NBR 14810 (2013) e ANSI A208.1 (2009). Realizou-se análise de variância (ANOVA) para testar a influência dos fatores individuais (densidade, percentual de adesivo e fração de Teca), além das interações entre tais fatores nas propriedades físico-mecânicas dos painéis. Os resultados apontaram para excelentes propriedades físicas e mecânicas dos painéis aglomerados de média e alta densidade, tendo resíduo de tinta, principalmente, nas proporções de 30 e 40%. Na maioria dos casos as propriedades de tais painéis foram superiores aos requisitos estipulados pela norma brasileira e pelas internacionais. Assim, ficou confirmada a viabilidade de produção dos aglomerados com pelo menos um dos insumos estudados bem como seu potencial de emprego para as finalidades compatíveis com produtos desta natureza.The use of products from renewable sources and free of toxic substances is a global trend, the proof is the steady increase in demand for wood-based products. According to the Forest Products Statistics (2015), world production of reconstituted wood panels in 2014 was 388 million cubic meters, an increase of 5.5% compared to the previous year and an increase of 34% compared to 2010. However, the industrial sector of wood panels for decades faces a major challenge with regard to toxic emissions coming from conventional adhesives. Faced with these problems, the purpose of this study was to test the feasibility of production of panels and OSB panels, with significant reduction of formaldehyde emissions from wood waste Pinus sp. and teak (Teak). In this sense, we sought to contribute to the increase of scientific knowledge on the use of natural polymer polyhydroxybutyrate (PHB) and residual ink resin-based epoxy as alternative adhesives. The panels were manufactured by varying the production parameters to obtain the best processing conditions, namely: low density, medium and high; resin content of 20, 30 and 40%; adding particles of Teak in proportions of 0, 25, 50, 75, 100%. The physical-mechanical performance of the panels was evaluated based on the standards NBR 14810 (2013) and ANSI A208.1 (2009). Held analysis of variance (ANOVA) to test the influence of individual factors (density, adhesive percentage and fraction Teak), and the interactions among these factors in the physical-mechanical properties of the panels. The results showed excellent physical and mechanical properties of the panels average clusters and high density, and ink residue, mainly in the proportions of 30 and 40%. In most cases the properties of these boards were superior to the requirements set by the Brazilian and international standards. Thus, it was confirmed production of agglomerates with at least one viability of inputs studied as well as their potential for employment for purposes compatible with products of this nature.
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Aroge, Olatunde O. "Assessment Of Disruption Risk In Supply Chain The Case Of Nigeria’s Oil Industry." Thesis, University of Bradford, 2018. http://hdl.handle.net/10454/17396.
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evaluate disruption risks in the supply chain of petroleum production. This methodology is developed to formalise and facilitate the systematic integration and implementation of various models; such as analytical hierarchy process (AHP) and partial least squares structural equation model (PLS-SEM) and various statistical tests. The methodology is validated with the case of Nigeria’s oil industry.
The study revealed the need to provide a responsive approach to managing the influence of geopolitical risk factors affecting supply chain in the petroleum production industry. However, the exploration and production risk, and geopolitical risk were identified as concomitant risk factors that impact performance in Nigeria’s oil industry. The research findings show that behavioural-based mechanisms successfully predict the ability of the petroleum industry to manage supply chain risks. The significant implication for this study is that the current theoretical debate on the supply chain risk management creates the understanding of agency theory as a governing mechanism for supply chain risk in the Nigerian oil industry. The systematic approach results provide an insight and objective information for decisions-making in resolving disruption risk to the petroleum supply chain in Nigeria. Furthermore, this study highlights to stakeholders on how to develop supply chain risk management strategies for mitigating and building resilience in the supply chain in the Nigerian oil industry.
The developed systematic method is associated with supply chain risk management and performance measure. The approach facilitates an effective way for the stakeholders to plan according to their risk mitigation strategies. This will consistently help the stakeholders to evaluate supply chain risk and respond to disruptions in supply chain. This capability will allow for efficient management of supply chain and provide the organization with quicker response to customer needs, continuity of supply, lower costs of operations and improve return on investment in the Nigeria oil industry. Therefore, the methodology applied provide a new way for implementing good practice for managing disruption risk in supply chain. Further, the systematic approach provides a simplistic modelling process for disruption risk evaluation for researchers and oil industry professionals. This approach would develop a holistic procedure for monitoring and controlling disruption risk in supply chains practices in Nigeria.
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Liu, Hangcheng. "Comparing Welch's ANOVA, a Kruskal-Wallis test and traditional ANOVA in case of Heterogeneity of Variance." VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/3985.
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Analysis of variance (ANOVA) is a robust test against the normality assumption, but it may be inappropriate when the assumption of homogeneity of variance has been violated. Welch ANOVA and the Kruskal-Wallis test (a non-parametric method) can be applicable for this case. In this study we compare the three methods in empirical type I error rate and power, when heterogeneity of variance occurs and find out which method is the most suitable with which cases including balanced/unbalanced, small/large sample size, and/or with normal/non-normal distributions.
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Veleba, Ondřej. "Studium vlivu složení na mechanické vlastnosti vysokohodnotného betonu." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2008. http://www.nusl.cz/ntk/nusl-216217.
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This work is devoted to study the influence of the composition on mechanical properties of high performance concret based on portland cement. 29 samples of high performance concrete (HPC) warying in composition were prepared. The constituents used for HPC preparation were: cement Aalborg White, silica fume, finelly ground blast furnace slag, finelly ground silica, calcinated bauxite and polycarboxylate based superplasticizer. The mechanical parameters (flexural and compressive strength) of the samples were observed after 7 and 28 days of moist curing. Compressive strength values after 28 days were in the range of 92 to 194 MPa and the flexural strength values were in the range of 7 to 23 MPa (without using of fiber reinforcement). The graphs showing mechanical parameters depending on the mixture composition were constructed and consequently evaluated.
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Léal, Françoise. "Etude de la production et de l'émanation de composés volatils malodorants sur textile à usage sportif." Thesis, Vandoeuvre-les-Nancy, INPL, 2011. http://www.theses.fr/2011INPL070N/document.
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Si la sueur fraîchement émise par le corps humain est inodore, la dégradation de celle-ci par la flore bactérienne cutanée produit des composés volatils malodorants, responsables des odeurs de transpiration. Les odeurs de transpiration apparaissent également sur les vêtements au cours de leur utilisation, particulièrement sur les textiles réalisés en fibres synthétiques. Ce travail a pour but d’améliorer la compréhension du phénomène d’émanation d’odeurs en étudiant l’effet du sujet testé, l’effet de la flore bactérienne et l’effet du textile sur les émissions de composés volatils malodorants.L’intérêt de ce travail réside dans l’approche globale de la problématique des odeurs de transpiration et dans la diversité des méthodes de mesure mises en place, tant dans l’étude de la flore microbiologique que dans les méthodes de mesures des composés odorants émis.Dans un premier temps, le dénombrement simultané de la flore bactérienne sur la peau et sur le vêtement a été réalisé sur un échantillon de 15 sujets à l’issue d’un exercice physique. Cette expérimentation a permis d’évaluer le taux de transfert bactérien moyen lors d’une activité sportive et d’étudier son rôle dans l’émission d’odeurs. Ensuite, afin d’affiner ces résultats, une méthode basée sur la biologie moléculaire a été mise en place pour réaliser le suivi qualitatif de la stabilité de la flore commensale axillaire d’un sujet pendant 3 mois. Le transfert bactérien spécifique entre la peau du testeur et le vêtement a été étudié pour 4 matières textiles sélectionnées (dont le coton et le PET). Ceci a permis de déterminer le rôle du transfert bactérien spécifique dans l’émission des odeurs à partir de textile.Enfin, le dernier chapitre est consacré à l’étude de l’émission de composés volatils et odorants à l’aide de mesures olfactives et d’un nez électronique au cours du temps par 8 composants textiles sélectionnés. Après traitement statistique par analyse en composante principale et étude détaillée des mesures, 9 composés chimiques ont été identifiés comme indicateurs d’un comportement textile malodorant. Ces derniers pourraient être utilisés dans la mise en place d’une méthode ciblée de mesure physico-chimique des mauvaises odeurs.Ce travail a permis de déterminer l’impact de chacun des facteurs sujet, flore bactérienne et textile dans l’émission d’odeurs. En outre, ce travail ouvre des perspectives sur l’étude des contaminations bactériennes par contact, mais également dans l’étude des odeurs, sur les phénomènes de désorption de molécules volatiles à partir de différentes matrices textiles et sur les solutions pouvant être envisagées pour limiter les émissions odorantes à partir de textilesFresh human sweat is odorless. Odoriferous volatile compounds are produced by the metabolism of bacteria living on the skin, generating strong malodor. Sweaty body odors do also appear on clothes during use, and especially on synthetic fabrics. The aim of this document is to improve understanding of odor emission by investigating subject effect, microbiota effect and fabric effect on the emission of odoriferous volatile compounds.Odors of perspiration are hereby globally approached with a wide use of methods and experimental devices, for microbial flora study as well as for odoriferous volatile compounds emission study.First, microflora enumeration has been simultaneously processed on the skin and on the fabric after exercise for 15 subjects. This experiment allowed an evaluation of the average bacterial transfer yield during physical activity and the beginning of the investigation of its effect on odor emission.A molecular biology methodology has then been developed in order to refine these results. Monitoring of qualitative composition of the microbiota has been performed to study the stability of the armpit’s ecosystem on a subject during 3 months. Specific microbial transfer from subject’s skin to clothe has been performed for 4 textile fabrics (including cotton and PET). This leaded to characterize the effect of specific bacterial transfer on odor emission from fabric.The last chapter is dedicated to the study of the emission of odoriferous volatile compounds over time using olfactory measurements and electronic nose for 8 selected fabrics. Principal component analysis targeted 9 chemical compounds that have been selected as malodorous behavior indicators for a given fabric. Those 9 compounds could be used for setting up a fitted physicochemical method of malodor.To conclude, this study helped to understand the effect of 3 factors in odor perception from a fabric after sport : subject, microbial flora and fabric. Perspectives have been charted on contact microbial contamination, but also on odor, and especially on desorption of odoriferous volatile molecules from a textile or knitted matrix. The solutions that could be used to limit malodorous emission from fabrics have also been discussed
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Krummenauer, Alex. "Desenvolvimento e validação de metodologia analítica para análise de aços por espectrometria de fluorescência de raios X por dispersão de energia (EDXRF)." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/178232.
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O desenvolvimento e validação de métodos analíticos é um procedimento necessário quando um método não normalizado é utilizado por um laboratório de ensaios. A validação de métodos também é um requisito específico da norma ABNT NBR ISO/IEC 17025, que determina os requisitos gerais para a competência dos laboratórios de ensaio e calibração. O objetivo da validação é demonstrar que o método analítico, nas condições em que é executado, produz resultados com a exatidão requerida. O Laboratório de Corrosão, Proteção e Reciclagem de Materiais (LACOR), da UFRGS, tem o ensaio de determinação de metais por fluorescência de raios X, acreditado pelo CGCRE/INMETRO, conforme ABNT NBR ISO/IEC 17025. O ensaio é feito usando o método de espectrometria de fluorescência de raios X por dispersão de energia (EDXRF). Este método, contudo, não é normalizado e, portanto, o mesmo foi validado, neste trabalho de pesquisa, para atender a este requisito. A validação foi feita com base no documento orientativo DOQ-CGCRE-08 e no guia EURACHEM. Os parâmetros de validação, para o ensaio quantitativo por EDXRF, que foram calculados neste trabalho são: seletividade; limite de detecção (LD) e limite de quantificação (LQ); linearidade e faixa de trabalho; veracidade de medição (tendência, erro normalizado, Z-score e comparação com método de referência) e precisão (repetibilidade, precisão intermediária e reprodutibilidade). Além disso, foi desenvolvida uma metodologia de cálculo de incerteza de medição para o ensaio por EDXRF Os resultados obtidos neste estudo demonstram que o método EDXRF, usado na determinação de metais em aços, é um método não normalizado validado e compatível com os resultados obtidos com os métodos de referência: espectrometria de fluorescência de raios X por dispersão de comprimento de onda (WDXRF), fotométricos e espectrometria de absorção atômica (AAS). Inclusive, o WDXRF é um método de referência usado em muitas normas internacionais, que descrevem métodos de análise de aços por fluorescência de raios X, como ASTM E572 ou ASTM E1085. O estudo desenvolvido nesta dissertação permitiu que o LACOR mantivesse sua acreditação no ensaio de determinação de metais por fluorescência de raios X, na avaliação do CGCRE/INMETRO, no presente ano. Outros frutos deste trabalho foram a confecção das curvas de calibração do espectrômetro NITON XL3t GOLDD+ e a revisão do procedimento de ensaio, onde esses novos conhecimentos sobre a técnica EDXRF foram aplicados. Futuramente, este trabalho pode ser usado por outros pesquisadores para desenvolver estudos em outras matrizes metálicas, como cobre, alumínio, titânio ou níquel, e, também, em outras áreas de aplicação como jóias, reciclagem de materiais metálicos ou, até mesmo, para análise elementar de resíduos retidos em membranas de troca iônica.The development and validation of analytical methods is a required procedure when a non-standard method is used by a testing laboratory. Method validation is also a specific requirement of the ABNT NBR ISO / IEC 17025, which determines the general requirements for the competence of testing and calibration laboratories. The purpose of validation is to demonstrate that the analytical method, under the conditions in which it is performed, produces results with the required accuracy. The Corrosion, Protection and Recycling Materials Laboratory (LACOR), at UFRGS, has the X-ray fluorescence metal analysis, accredited by CGCRE / INMETRO, according to ABNT NBR ISO / IEC 17025. The test is performed using Energy Dispersive X-Ray Fluorescence spectrometry, EDXRF method. This method, however, is not standardized; therefore, it was validated in this research to meet this requirement. The validation was based on the DOQ-CGCRE-08 document and the EURACHEM guide. The method performance calculated in this study for quantitative testing by EDXRF are: selectivity; limit of detection (LOD) and limit of quantification (LOQ); linearity and working range; trueness (bias, normalized error, Z-score and comparison with reference method) and precision (repeatability, intermediate precision and reproducibility). In addition, a measurement uncertainty calculation methodology was developed for the EDXRF testing The results obtained in this study demonstrate that the EDXRF method, used in the determination in the chemical analysis of steels, is a validated non-standard method and compatible with the results obtained with the reference methods: Wavelength Dispersive X-Ray Fluorescence spectrometry (WDXRF), photometric and atomic absorption spectrometry (AAS). In addition, WDXRF is a reference method used in many international standards, which describes analysis of steels by X-ray fluorescence spectrometry such ASTM E572 or ASTM E1085. The study developed in this dissertation allowed LACOR to maintain its accreditation in the test of metal by X-ray fluorescence analysis, in the CGCRE / INMETRO audit, this year. Other fruits of this work were the preparation of calibration curves of NITON XL3t GOLDD + spectrometer and complete revision of testing procedure, where this new knowledge about the EDXRF technique was applied. In the future, this work can be used by other researchers to develop studies in other base metals such as copper, aluminum, titanium or nickel, and also in other areas of application such as jewelry, recycling of metallic materials or even for analysis elemental residues retained in ion exchange membranes.
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Touzani, Samir. "Méthodes de surface de réponse basées sur la décomposition de la variance fonctionnelle et application à l'analyse de sensibilité." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00614038.
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L'objectif de cette thèse est l'investigation de nouvelles méthodes de surface de réponse afin de réaliser l'analyse de sensibilité de modèles numériques complexes et coûteux en temps de calcul. Pour ce faire, nous nous sommes intéressés aux méthodes basées sur la décomposition ANOVA. Nous avons proposé l'utilisation d'une méthode basée sur les splines de lissage de type ANOVA, alliant procédures d'estimation et de sélection de variables. L'étape de sélection de variable peut devenir très coûteuse en temps de calcul, particulièrement dans le cas d'un grand nombre de paramètre d'entrée. Pour cela nous avons développé un algorithme de seuillage itératif dont l'originalité réside dans sa simplicité d'implémentation et son efficacité. Nous avons ensuite proposé une méthode directe pour estimer les indices de sensibilité. En s'inspirant de cette méthode de surface de réponse, nous avons développé par la suite une méthode adaptée à l'approximation de modèles très irréguliers et discontinus, qui utilise une base d'ondelettes. Ce type de méthode a pour propriété une approche multi-résolution permettant ainsi une meilleure approximation des fonctions à forte irrégularité ou ayant des discontinuités. Enfin, nous nous sommes penchés sur le cas où les sorties du simulateur sont des séries temporelles. Pour ce faire, nous avons développé une méthodologie alliant la méthode de surface de réponse à base de spline de lissage avec une décomposition en ondelettes. Afin d'apprécier l'efficacité des méthodes proposées, des résultats sur des fonctions analytiques ainsi que sur des cas d'ingénierie de réservoir sont présentées.
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Oakley, Florence. "Generational differences in the frequency and importance of meaningful work." Thesis, University of Canterbury. Department of Management, 2015. http://hdl.handle.net/10092/10931.
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This thesis aimed to investigate generational differences in the frequency and importance of meaningful work in employees based on the 7 facets of the Map of Meaning. Hypotheses were tested through Analysis of Variance of secondary data. 395 participants self-reported levels of meaningful work on the Comprehensive Meaningful Work Scale. Results indicated that Generation Y had significantly lower levels of meaningful work. Generation Y had significantly lower levels of Unity (importance), Serving (frequency and importance), Expressing full potential (frequency), Reality (frequency and importance) and Inspiration (frequency). Significant differences occurred mainly between Generation Y and Baby boomers, with some significant differences between Generation Y and Generation X and no significant differences between Generation X and Baby boomers. Results showed that overall frequency and importance levels were significantly lower for Generation Y. Overall frequency levels were lower than overall importance levels, which suggests that employees’ desire for meaningful work may not be satisfied. In light of this evidence, it is suggested that to improve organisational outcomes such as engagement, retention and performance, managers should provide opportunities for employees to engage in meaningful work with particular focus on Generation Y. Employees themselves should take responsibility to find meaning in their own work and life because engagement in meaningful activities can lead to satisfaction, belonging, fulfilment and a better understanding of one’s purpose in life.
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Ramazi, Pouria. "Variance Analysis of Parallel Hammerstein Models." Thesis, KTH, Reglerteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-102169.
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In this thesis we generalize some recent results on variance analysis of Hammerstein models. A variance formula for an arbitrary number of parallel blocks is derived. This expression shows that the variance increases in one block due to the estimation of parameters in other blocks but levels off when the number of parameters in other blocks reach the number of parameters in that block. As a second contribution, the problem of how to design the input so that the identification process leads to a more accurate model is considered. In other words, how to choose the input signal so that the model error described previously is minimized, is studied. The investigations show that the optimal input probability density function has a surprisingly simple format. In summary, some of the derived results can be used directly in practice, while some might be used for further research.
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Zoglat, Abdelhak. "Analysis of variance for functional data." Thesis, University of Ottawa (Canada), 1994. http://hdl.handle.net/10393/10136.
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In this dissertation we present an extension to the well known theory of multivariate analysis of variance. In various situations data are continuous stochastic functions of time or space. The speed of pollutants diffusing through a river, the real amplitude of a signal received from a broadcasting satellite, or the hydraulic conductivity rates at a given region are examples of such processes. After the mathematical background we develop tools for analyzing such data. Namely, we develop estimators, tests, and confidence sets for the parameters of interest. We extend these results, obtained under the normality assumption, and show that they are still valid if this assumption is relaxed. Some examples of applications of our techniques are given. We also outline how the latter can apply to random and mixed models for continuous data. In the appendix, we give some programs which we use to compute the distributions of some of our tests statistics.
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Adnan, Arisman. "Analysis of taste-panel data using ANOVA and ordinal logistic regression." Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402150.
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Liu, Yuan. "Mixed anova model analysis of microarray experiments with locally polled error /." Electronic version (PDF), 2004. http://dl.uncw.edu/etd/2004/liuy/yuanliu.pdf.
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Di, Gessa Giorgio. "Simple strategies for variance uncertainty in meta-analysis." Connect to e-thesis, 2007. http://theses.gla.ac.uk/128/.
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Thesis (M.Sc.(R)) - University of Glasgow, 2007.M.Sc.(R) thesis submitted to the Department of Statistics, Faculty of Information and Mathematical Sciences, University of Glasgow, 2007. Includes bibliographical references. Print version also available.
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Chao, Jackson Sheng-Kuang. "Analysis of variance impact on manufacturing flow time." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13339.
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Thesis (M.S.)--Massachusetts Institute of Technology, Sloan School of Management, 1991, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1991.Includes bibliographical references (leaves 119-120).
by Jackson Sheng-Kuang Chao.
M.S.
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Pathiravasan, Chathurangi Heshani Karunapala. "Generalized Semiparametric Approach to the Analysis of Variance." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/dissertations/1702.
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The one-way analysis of variance (ANOVA) is mainly based on several assumptions and can be used to compare the means of two or more independent groups of a factor. To relax the normality assumption in one-way ANOVA, recent studies have considered exponential distortion or tilt of a reference distribution. The reason for the exponential distortion was not investigated before; thus the main objective of the study is to closely examine the reason behind it. In doing so, a new generalized semi-parametric approach for one-way ANOVA is introduced. The proposed method not only compares the means but also variances of any type of distributions. Simulation studies show that proposed method has favorable performance than classical ANOVA. The method is demonstrated on meteorological radar data and credit limit data. The asymptotic distribution of the proposed estimator was determined in order to test the hypothesis for equality of one sample multivariate distributions. The power comparison of one sample multivariate distributions reveals that there is a significant power improvement in the proposed chi-square test compared to the Hotelling's T-Square test for non normal distributions. A bootstrap paradigm is incorporated for testing equidistributions of multiple samples. As far as power comparison simulations for multiple large samples are considered, the proposed test outperforms other existing parametric, nonparametric and semi-parametric approaches for non normal distributions.
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Nisa, Khoirin. "On multivariate dispersion analysis." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2025.
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Cette thèse examine la dispersion multivariée des modelés normales stables Tweedie. Trois estimateurs de fonction variance généralisée sont discutés. Ensuite dans le cadre de la famille exponentielle naturelle deux caractérisations du modèle normal-Poisson, qui est un cas particulier de modèles normales stables Tweedie avec composante discrète, sont indiquées : d'abord par fonction variance et ensuite par fonction variance généralisée. Le dernier fournit la solution à un problème particulier d'équation de Monge-Ampère. Enfin, pour illustrer l'application de la variance généralisée des modèles Tweedie stables normales, des exemples à partir des données réelles sont fournisThis thesis examines the multivariate dispersion of normal stable Tweedie (NST) models. Three generalize variance estimators of some NST models are discussed. Then within the framework of natural exponential family, two characterizations of normal Poisson model, which is a special case of NST models with discrete component, are shown : first by variance function and then by generalized variance function. The latter provides a solution to a particular Monge-Ampere equation problem. Finally, to illustrate the application of generalized variance of normal stable Tweedie models, examples from real data are provided
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Khalilzadeh, Amir Hossein. "Variance Dependent Pricing Kernels in GARCH Models." Thesis, Uppsala universitet, Analys och tillämpad matematik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-180373.
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Bourahima, Fazati. "Évolutions microstructurales et défauts générés par laser cladding lors du dépôt de Ni sur des moules de verrerie en alliage de Cu-Ni-Al et en fonte GL." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS017/document.
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Dans l’industrie de la verrerie, le laser cladding est une technique de rechargement très innovante permettant de déposer une couche très fine d’un alliage à base de nickel pour protéger les moules (utiles à la fabrication de bouteilles en verre) de la corrosion, de l’abrasion ainsi que de la fatigue thermique. La méthode utilisée ici (fusion de poudre projetée par laser) est très courante en fabrication additive. Cette étude s’intéresse à l’impact du rechargement sur le dépôt et les substrats en Cu-Ni-Al et en fonte GL. L’influence sur la microstructure ainsi que sur le comportement mécanique a pu être étudiée (MEB et microanalyses, dureté, contraintes résiduelles ...). Nous nous sommes focalisés sur l’apparition de défauts tels que le manque d’accroche lors du laser cladding sur du Cu-Ni-Al et sur la possible fissuration lors du rechargement sur de la fonte GL. Le but est bien sûr de s’affranchir de ces défauts. Il a notamment été mis en évidence que le manque d’accroche (cas du Cu-Ni-Al) est lié à la distribution gaussienne de la poudre qui atténue la puissance incidente du laser au niveau du pic de poudre. Le manque d'accroche n'est pas détecté sur le substrat en fonte en raison de sa forte absorptivité et de sa faible conductivité thermique. Néanmoins, des fissures peuvent être observées en raison de contraintes résiduelles thermiques et de la présence d'une zone affectée thermiquement. De plus, l’analyse statistique ANOVA a permis une optimisation des paramètres de rechargement de telle sorte à obtenir une accroche dans toute la section tout en respectant les préconisations géométriques données par les Établissements CHPOLANSKY pour le cordonIn glass industry, the laser cladding is an innovative surfacing technique allowing to deposit a very thin layer of nickel to protect glass mold (useful for glass bottle production) against corrosion, abrasion and thermal fatigue. This method (powder fusion by projection) is well known in additive manufacturing. The aim of this work is to observe the impact of the laser cladding on the coating behavior but also on the Cu-Ni-Al and flake-graphite cast iron substrates. The microstructure and the mechanical properties were studied (SEM and microanalysis, microhardness, residual stress …) around the interface cladding/substrate. The work was also focused on the defects like lack of bonding but also on cracking behavior during surfacing on cast iron. The purpose was to prevent from those defects. This work showed that the lack of bonding to the Cu-Ni-Al substrate is due to the gaussian distribution of the powder which attenuates the input laser power at its peak. The lack of bonding is not detected on cast iron substrate thanks to its high absorptivity and low thermal conductivity. Nevertheless, cracks can be observed due to thermal residual stresses and the presence of a thermal affected zone. The ANOVA technique allowed us to optimize the processing parameters in order to obtain a perfect bonding and the geometry wanted by CHPOLANSKY Establishments
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Carter, Bruce Jerome. "An ANOVA Analysis of Education Inequities Using Participation and Representation in Education Systems." ScholarWorks, 2017. https://scholarworks.waldenu.edu/dissertations/4274.
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A problem recognized in the United States is that a K-12 public education in urban communities is more likely to support existing patterns of inequality than to serve as a pathway to opportunity. The specific focus of this research was on the poor academic performance in U.S K-12 urban communities. Using Benet's polarities of democracy theory as the foundation, the purpose of this correlational study was to determine which independent variables, enrollment rates, high school graduation rates, property tax funding rates for schools, teacher quality, and youth literacy rates are- statistically associated- with quality education outcomes by using the polarities of democracy participation and representation tenets as proxy variables. Secondary data spanning a 5-year aggregate period, 2010-2015, was compared for both Massachusetts and the United States, using Germany as the benchmark. Data were acquired from the Programme for International Student Assessment from the Organisation for Economic Cooperation and Development. The total sample included 150 cases randomly selected from 240 schools in Massachusetts and 150 schools in Germany. Data were analyzed using ANOVA. The results of this study indicate a statistically- significant (p- < .001) pairwise association between each of the 5 independent variables and the dependent variable. The 5 independent variables had a positive statistically significant effect on education quality. The implication for social change from this study includes insight and recommendations to the U.S Department of Education into best practices for reducing educational inequality and improving educational quality as measured by achievement in the United States.
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Lin, Yu-pin. "Multiple-point variance analysis for groundwater monitoring network design." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/19511.
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Chen, Yuh-Ing. "Nonparametric procedures for structured effects in analysis of variance /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487671108307997.
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Larsson, Stefan. "Mixing Processes for Ground Improvement by Deep Mixing." Doctoral thesis, KTH, Civil and Architectural Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3667.
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The thesis is dealing with mixing processes havingapplication to ground improvement by deep mixing. The mainobjectives of the thesis is to make a contribution to knowledgeof the basic mechanisms in mixing binding agents into soil andimprove the knowledge concerning factors that influence theuniformity of stabilised soil.
A great part of the work consists of a literature surveywith particular emphasis on literature on the processindustries. This review forms a basis for a profounddescription and discussion of the mixing process and factorsaffecting the process in connection with deep mixingmethods.
The thesis presents a method for a simple field test for thestudy of influential factors in the mixing process. A number offactors in the installation process of lime-cement columns havebeen studied in two field tests using statistical multifactorexperiment design. The effects of retrieval rate, number ofmixing blades, rotation speed, air pressure in the storagetank, and diameter of the binder outlet on the stabilisationeffect and the coefficient of variation determined byhand-operated penetrometer tests for excavated lime-cementcolumns, were studied.
The literature review, the description of the mixingprocess, and the results from the field tests provide a morebalanced picture of the mixing process and are expected to beuseful in connection to ground improvement projects and thedevelopment of mixing equipments.
The concept of sufficient mixture quality, i.e. theinteraction between the mixing process and the mechanicalsystem, is discussed in the last section. By means ofgeostatistical methods, the analysis considers thevolume-variability relationship with reference to strengthproperties. According to the analysis, the design values forstrength properties depends on the mechanical system, the scaleof scrutiny, the spatial correlation structure, and the conceptof safety, i.e. the concept of sufficient mixture quality isproblem specific.
Key words:Deep Mixing, Lime cement columns, Mixingmechanisms, Mixture quality, Field test, ANOVA, Variancereduction.
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Newton, Wesley E. "Data Analysis Using Experimental Design Model Factorial Analysis of Variance/Covariance (DMAOVC.BAS)." DigitalCommons@USU, 1985. https://digitalcommons.usu.edu/etd/6378.
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DMAOVC.BAS is a computer program written in the compiler version of microsoft basic which performs factorial analysis of variance/covariance with expected mean squares. The program accommodates factorial and other hierarchical experimental designs with balanced sets of data. The program is writ ten for use on most modest sized microprocessors, in which the compiler is available. The program is parameter file driven where the parameter file consists of the response variable structure, the experimental design model expressed in a similar structure as seen in most textbooks, information concerning the factors (i.e. fixed or random, and the number of levels), and necessary information to perform covariance analysis. The results of the analysis are written to separate files in a format that can be used for reporting purposes and further computations if needed.
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Meterelliyoz, Kuyzu Melike. "Variance parameter estimation methods with re-use of data." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26490.
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Thesis (Ph.D)--Industrial and Systems Engineering, Georgia Institute of Technology, 2009.Committee Co-Chair: Alexopoulos, Christos; Committee Co-Chair: Goldsman, David; Committee Member: Kim, Seong-Hee; Committee Member: Shapiro, Alexander; Committee Member: Spruill, Carl. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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馮子豪 and Tze-ho Fung. "Bootstrap estimation of variance in survey sampling." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1987. http://hub.hku.hk/bib/B31208198.
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Fung, Tze-ho. "Bootstrap estimation of variance in survey sampling /." [Hong Kong] : University of Hong Kong, 1987. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12362694.
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Yang, Yani. "Dimension reduction in the regressions through weighted variance estimation." HKBU Institutional Repository, 2009. http://repository.hkbu.edu.hk/etd_ra/1073.
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Wiedemann, Eric A. "Reducing variance between two systems by inducing correlation." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/23345.
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Hammi, Malik, and Ahmet Hakan Akdeve. "Poweranalys : bestämmelse av urvalsstorlek genom linjära mixade modeller och ANOVA." Thesis, Linköpings universitet, Statistik och maskininlärning, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-149026.
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In research where experiments on humans and animals is performed, it is in advance important to determine how many observations that is needed in a study to detect any effects in groups and to save time and costs. This could be examined by power analysis, in order to determine a sample size which is enough to detect any effects in a study, a so called “power”. Power is the probability to reject the null hypothesis when the null hypothesis is false. Mälardalen University and the Caroline Institute have in cooperation, formed a study (The Climate Friendly and Ecological Food on Microbiota) based on individual’s dietary intake. Every single individual have been assigned to a specific diet during 8 weeks, with the purpose to examine whether emissions of carbon dioxide, CO2, differs reliant to the specific diet each individuals follows. There are two groups, one treatment and one control group. Individuals assigned to the treatment group are supposed to follow a climatarian diet while the individuals in the control group follows a conventional diet. Each individual have been followed up during 8 weeks in total, with three different measurements occasions, 4 weeks apart. The different measurements are Baseline assessment, Midline assessment and End assessment. In the CLEAR-study there are a total of 18 individuals, with 9 individuals in each group. The amount of individuals are not enough to reach any statistical significance in a test and therefore the sample size shall be examined through power analysis. In terms of, data, every individual have three different measurements occasions that needs to be modeled through mixed-design ANOVA and linear mixed models. These two methods takes into account, each individual’s different measurements. The models which describes data are applied in the computations of sample sizes and power. All the analysis are done in the programming language R with means and standard deviations from the study and the models as a base. Sample sizes and power have been computed for two different linear mixed models and one ANOVA model. The linear mixed models required less individuals than ANOVA in terms of a desired power of 80 percent. 24 individuals in total were required by the linear mixed model that had the factors group, time, id and the covariate sex. 42 individuals were required by ANOVA that includes the variables id, group and time.Inom forskning där försök, dels utförs på människor och djur, vill man försäkra sig om en lämplig urvalsstorlek för att spara tid och kostnad samtidigt som en önskad statistisk styrka uppnås. Mälardalens högskola och Karolinska institutet har gjort en pilotstudie (CLEAR) som undersöker människors koldioxidutsläpp i förhållande till kosthållning. Varje individ i studien har fått riktlinjer om att antingen följa en klimatvänlig- eller en konventionell kosthållning i totalt 8 veckor. Individerna följs upp med 4 veckors mellanrum, vilket har resulterat i tre mättillfällen, inklusive en baslinjemätning. I CLEAR-studien finns variabler om individernas kön, ålder, kosthållning samt intag av makro- och mikronäringsämnen. Nio individer i respektive grupp finns, där grupperna är klimat- och kontrollgruppen. Totala antalet individer i pilotstudien är för få för att erhålla statistisk signifikans vid statistiska tester och därför bör urvalsstorleken undersökas genom att göra styrkeberäkningar. Styrkan som beräknas är sannolikheten att förkasta nollhypotesen när den är falsk. För att kunna beräkna urvalsstorlekar måste modeller skapas utifrån strukturen på data, vilket kommer att göras med metoderna mixed-design ANOVA och linjära mixade modeller. Metoderna tar hänsyn till att varje individ har fler än en mätning. Modellerna som beskriver data tillämpas i beräkningarna av styrka. Urvalsstorlekarna och styrkan som beräknats är simuleringsbaserad och har analyserats i programspråket R med modellerna och värden från pilotstudien som grund. Styrka och urvalsstorlekar har beräknats för två linjära mixade modeller och en ANOVA. De linjära mixade modellerna kräver färre individer än ANOVA för en önskad styrka på 80 procent. Av de linjära mixade modellerna som krävde minst individer behövdes totalt 24 individer medan mixed design-ANOVA krävde 42 individer totalt.
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Ellington, James Kemp. "Systematic Sources of Variance in Supervisory Job Performance Ratings: A Multilevel Analysis of Between-Rater and Between-Context Variance." NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-11022006-194219/.
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The appraisal of job performance is critical for both the practice of human resource management and organizational research. Furthermore, the most frequently used method for measuring performance is a supervisory rating. Given the prevalence of this method, it is crucial to understand the factors which influence rater behaviors. Recent research has indicated that a large portion of the variance in ratings is idiosyncratic to the rater (Scullen, Mount, & Goff, 2000). However, the nature of this idiosyncratic variance remains unclear. Previous models of appraisal have focused on either the cognitive processes involved, or more recently, the appraisal context. Although this recent focus on contextual issues has shown promise, the extent to which raters are influenced by the context in which they work is unknown. Therefore, the purpose of this research was to contribute to our understanding of supervisory ratings by incorporating a multilevel analytic approach in order to partition the variance between raters from the variance between contexts. This approach allowed for the investigation of several rater and context-level characteristics, in attempt to explain the variance associated with these two sources. More specifically, a conceptual model was proposed in order to examine rater-level variables including rater tendencies for leniency and halo, along with rater opportunities to observe performance. Contextual factors proposed for study included norms for leniency and halo, opportunities to observe performance at the context-level, and the nature of work/activity itself within various contexts. Moreover, this research incorporated a multidimensional performance criterion, in order to provide a more thorough investigation of the relationships of interest here. Results suggested that the rating context accounted for significant variance in both task and citizenship performance ratings. Furthermore, the rater tendency for leniency explained significant between-rater variation in both criteria. The rater tendency for halo was also significant, however this finding did not recur when analyzing a replication sample of data. At the context-level, the norm for leniency consistently predicted variance in citizenship performance, but was only a significant predictor of task performance in one sample. Finally, although these relationships were not consistent across samples, the nature of work/activity and the contextual norm for halo explained significant between-context variation in citizenship performance ratings. The interpretation and implications of these results are discussed, along with limitations of this research and suggestions for future research.
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Nagarajan, Balaji. "Analytic Evaluation of the Expectation and Variance of Different Performance Measures of a Schedule under Processing Time Variability." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31264.
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The realm of manufacturing is replete with instances of uncertainties in job processing times, machine statuses (up or down), demand fluctuations, due dates of jobs and job priorities. These uncertainties stem from the inability to gather accurate information about the various parameters (e.g., processing times, product demand) or to gain complete control over the different manufacturing processes that are involved. Hence, it becomes imperative on the part of a production manager to take into account the impact of uncertainty on the performance of the system on hand. This uncertainty, or variability, is of considerable importance in the scheduling of production tasks. A scheduling problem is primarily to allocate the jobs and determine their start times for processing on a single or multiple machines (resources) for the objective of optimizing a performance measure of interest. If the problem parameters of interest e.g., processing times, due dates, release dates are deterministic, the scheduling problem is relatively easier to solve than for the case when the information is uncertain about these parameters. From a practical point of view, the knowledge of these parameters is, most often than not, uncertain and it becomes necessary to develop a stochastic model of the scheduling system in order to analyze its performance.
Investigation of the stochastic scheduling literature reveals that the preponderance of the work reported has dealt with optimizing the expected value of the performance measure. By focusing only on the expected value and ignoring the variance of the measure used, the scheduling problem becomes purely deterministic and the significant ramifications of schedule variability are essentially neglected. In many a practical cases, a scheduler would prefer to have a stable schedule with minimum variance than a schedule that has lower expected value and unknown (and possibly high) variance. Hence, it becomes apparent to define schedule efficiencies in terms of both the expectation and variance of the performance measure used. It could be easily perceived that the primary reasons for neglecting variance are the complications arising out of variance considerations and the difficulty of solving the underlying optimization problem. Moreover, research work to develop closed-form expressions or methodologies to determine the variance of the performance measures is very limited in the literature. However, conceivably, such an evaluation or analysis can only help a scheduler in making appropriate decisions in the face of uncertain environment. Additionally, these expressions and methodologies can be incorporated in various scheduling algorithms to determine efficient schedules in terms of both the expectation and variance.
In our research work, we develop such analytic expressions and methodologies to determine the expectation and variance of different performance measures of a schedule. The performance measures considered are both completion time and tardiness based measures. The scheduling environments considered in our analysis involve a single machine, parallel machines, flow shops and job shops. The processing times of the jobs are modeled as independent random variables with known probability density functions. With the schedule given a priori, we develop closed-form expressions or devise methodologies to determine the expectation and variance of the performance measures of interest. We also describe in detail the approaches that we used for the various scheduling environments mentioned earlier. The developed expressions and methodologies were programmed in MATLAB R12 and illustrated with a few sample problems. It is our understanding that knowing the variance of the performance measure in addition to its expected value would aid in determining the appropriate schedule to use in practice. A scheduler would be in a better position to base his/her decisions having known the variability of the schedules and, consequently, can strike a balance between the expected value and variance.Master of Science
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Marshall, Williams S. IV. "Robust variance estimation for ranking and selection." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/24263.
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Chan, Iok Ip. "Analysis of variance and its applications in Macao educational researches." Thesis, University of Macau, 2007. http://umaclib3.umac.mo/record=b1687709.
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Langan, Dean. "Estimating the heterogeneity variance in a random-effects meta-analysis." Thesis, University of York, 2015. http://etheses.whiterose.ac.uk/13507/.
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In a meta-analysis, differences in the design and conduct of studies may cause variation in effects beyond what is expected from chance alone. This additional variation is commonly known as heterogeneity, which is incorporated into a random-effects model. The heterogeneity variance parameter in this model is commonly estimated by the DerSimonian-Laird method, despite being shown to produce negatively biased estimates in simulated data. Many other methods have been proposed, but there has been less research into their properties. This thesis compares all methods to estimate the heterogeneity variance in both empirical and simulated meta-analysis data. First, methods are compared in 12,894 empirical meta-analyses from the Cochrane Database of Systematic Reviews (CDSR). These results showed high discordance in estimates of the heterogeneity variance between methods, so investigating their properties in simulated meta-analysis data is worthwhile. A systematic review of relevant simulation studies was then conducted and identified 12 studies, but there was little consensus between them and conclusions could only be considered tentative. A new simulation study was conducted in collaboration with other statisticians. Results confirmed that the DerSimonian-Laird method is negatively biased in scenarios where within-study variances are imprecise and/or biased. On the basis of these results, the REML approach to heterogeneity variance estimation is recommended. A secondary analysis combines simulated and empirical meta-analysis data and shows all methods usually have poor properties in practice; only marginal improvements are possible using REML. In conclusion, caution is advised when interpreting estimates of the heterogeneity variance and confidence intervals should always be presented to express its uncertainty. More promisingly, the Hartung-Knapp confidence interval method is robust to poor heterogeneity variance estimates, so sensitivity analysis is not usually required for inference on the mean effect.
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Seppala, Christopher Toomath. "Dynamic analysis of variance methods for monitoring control system performance." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0006/NQ42975.pdf.
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