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Dissertations / Theses on the topic 'Overdispersion'

Author: Grafiati

Published: 4 June 2021

Last updated: 25 July 2025

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1

Crouchley, Robert. "Testing for overdispersion in the parametric proportional hazards and some related models." Thesis, Imperial College London, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403689.

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Zheng, Shuo. "New Hierarchical Nonlinear Modeling for Count Data: Estimation and Testing in The Presence of Overdispersion." Diss., Temple University Libraries, 2011. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/132533.

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Statistics<br>Ph.D.<br>In studies of traffic accidents, disease occurrence, mismatches in genetic code and impact of pollution on ecological communities the key observational variable is often a count. For example, daily counts of accidents on a segment of highway will vary with weather and other traffic conditions: highway engineers seek to relate accident counts to these roadway conditions. Formal statistical analysis of this kind of data is critically dependent on using the correct model for the random count data. However, statistical analysis packages use only those random count models tha

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Davidson, Christopher L. "A Model Selection Paradigm for Modeling Recurrent Adenoma Data in Polyp Prevention Trials." Thesis, The University of Arizona, 2012. http://hdl.handle.net/10150/228465.

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Colorectal polyp prevention trials (PPTs) are randomized, placebo-controlled clinical trials that evaluate some chemo-preventive agent and include participants who will be followed for at least 3 years to compare the recurrence rates (counts) of adenomas. A large proportion of zero counts will likely be observed in both groups at the end of the observation period. Poisson general linear models (GLMs) are usually employed for estimation of recurrence in PPTs. Other models, including the negative binomial (NB2), zero-inflated Poisson (ZIP), and zero-inflated negative binomial (ZINB) may be bette

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Kreider, Scott Edwin Douglas. "A case study in handling over-dispersion in nematode count data." Manhattan, Kan. : Kansas State University, 2010. http://hdl.handle.net/2097/4248.

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5

Rocha, Everton Batista da. "Modelos para a análise de dados de contagens longitudinais com superdispersão: estimação INLA." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/11/11134/tde-05112015-144057/.

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Em ensaios clínicos é muito comum a ocorrência de dados longitudinais discretos. Para sua análise é necessário levar em consideração que dados observados na mesma unidade experimental ao longo do tempo possam ser correlacionados. Além dessa correlação inerente aos dados é comum ocorrer o fenômeno de superdispersão (ou sobredispersão), em que, existe uma variabilidade nos dados além daquela captada pelo modelo. Um caso que pode acarretar a superdispersão é o excesso de zeros, podendo também a superdispersão ocorrer em valores não nulos, ou ainda, em ambos os casos. Molenberghs, Verbeke e Demétr

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Silva, Andreza Jardelino da. "Modelos para análise de dados superdispersos de indução de haploidia em milho." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/11/11134/tde-20072017-133448/.

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O milho é uma espécie alógama cujo produto comercial são os híbridos, os quais originam-se do cruzamento de duas linhagens endogâmicas. Uma forma para obtenção de tais linhagens é por meio das técnicas de indução de haploidia e posterior obtenção dos duplo-haploides, permitindo até 100% de homozigose. Essas técnicas retornam resultados importantes no melhoramento de milho. Uma variável de interesse importante, obtida a partir dessas técnicas é a taxa de indução de haploidia, a qual trata-se de uma proporção entre o número de sementes haploides e o número total de sementes. O conjunto de dados

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Ibukun, Michael Abimbola. "Modely s Touchardovým rozdělením." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-445468.

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In 2018, Raul Matsushita, Donald Pianto, Bernardo B. De Andrade, Andre Cançado & Sergio Da Silva published a paper titled ”Touchard distribution”, which presented a model that is a two-parameter extension of the Poisson distribution. This model has its normalizing constant related to the Touchard polynomials, hence the name of this model. This diploma thesis is concerned with the properties of the Touchard distribution for which delta is known. Two asymptotic tests based on two different statistics were carried out for comparison in a Touchard model with two independent samples, supported by s

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Oesselmann, Clarissa Cardoso. "Equações de estimação generalizadas com resposta binomial negativa: modelando dados correlacionados de contagem com sobredispersão." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-06072017-122423/.

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Uma suposição muito comum na análise de modelos de regressão é a de respostas independentes. No entanto, quando trabalhamos com dados longitudinais ou agrupados essa suposição pode não fazer sentido. Para resolver esse problema existem diversas metodologias, e talvez a mais conhecida, no contexto não Gaussiano, é a metodologia de Equações de Estimação Generalizadas (EEGs), que possui similaridades com os Modelos Lineares Generalizados (MLGs). Essas similaridades envolvem a classificação do modelo em torno de distribuições da família exponencial e da especificação de uma função de variância. A

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9

Lora, Mayra Ivanoff. "Modelos de regressão beta-binomial/poisson para contagens bivariadas." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-09062011-095707/.

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Propomos um modelo Beta-Binomial/Poisson para dados provenientes de um estudo com doentes de Parkinson, que consistiu em contar durante um minuto quantas tarefas foram realizadas e destas, quantas de maneira correta, antes e depois de um treinamento. O objetivo era verificar se o treinamento aumentava o número de tentativas e a porcentagem de acerto, o que destaca o aspecto bivariado do problema. Esse modelo considera tal aspecto, usa uma distribuição mais adequada a dados de contagem e ainda suporta a sobredispersão presente nos dados. Obtemos estimadores de máxima verossimilhança dos parâmet

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Lora, Mayra Ivanoff. "Modelos Beta-Binomial/Poisson-Gama para contagens bivariadas repetidas." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-27082009-120419/.

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Em Lora e Singer (Statistics in Medicine, 2008), propusemos um modelo Beta- Binomial/Poisson p-variado para análise dos dados provenientes de um estudo que consistiu em contar o número de tentativas e acertos de um exercício manual com duração de um minuto realizado por doentes de Parkinson, antes e depois de um treinamento. O objetivo era verificar se o treinamento aumentava o número de tentativas e a porcentagem de acerto, o que destaca o aspecto bivariado do problema. Esse modelo leva tais características em consideração, usa uma distribuição adequada para dados de contagem e ainda acomoda

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Nati, Lilian. "Superdispersão em dados binomiais hierárquicos." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-19062008-132744/.

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Para analisar dados binários oriundos de uma estrutura hierárquica com dois níveis (por exemplo, aluno e escola), uma alternativa bastante utilizada é a suposição da distribuição binomial para as unidades experimentais do primeiro nível (aluno) condicionalmente a um efeito aleatório proveniente de uma distribuição normal para as unidades do segundo nível (escola). Neste trabalho, propõe-se a adição de um efeito aleatório normal no primeiro nível de um modelo linear generalizado hierárquico binomial para contemplar uma possível variabilidade extra-binomial decorrente da dependência entre os ens

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Bhaktha, Nivedita. "Properties of Hurdle Negative Binomial Models for Zero-Inflated and Overdispersed Count data." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1543573678017356.

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Pirozhkova, Daria. "Statistical models for an MTPL portfolio." Master's thesis, Vysoká škola ekonomická v Praze, 2017. http://www.nusl.cz/ntk/nusl-359373.

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In this thesis, we consider several statistical techniques applicable to claim frequency models of an MTPL portfolio with a focus on overdispersion. The practical part of the work is focused on the application and comparison of the models on real data represented by an MTPL portfolio. The comparison is presented by the results of goodness-of-fit measures. Furthermore, the predictive power of selected models is tested for the given dataset, using the simulation method. Hence, this thesis provides a combination of the analysis of goodness-of-fit results and the predictive power of the models.

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Vaudor, Lise. "Estimation de la moyenne et de la variance de l’abondance de populations en écologie à partir d’échantillons de petite taille." Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10013/document.

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En écologie comme dans bien d’autres domaines, les échantillons de données de comptage comprennent souvent de nombreux zéros et quelques abondances fortes. Leur distribution est particulièrement surdispersée et asymétrique. Les méthodes les plus classiques d’inférence sont souvent mal adaptées à ces distributions, à moins de disposer d’échantillons de très grande taille. Il est donc nécessaire de s’interroger sur la validité des méthodes d’inférence, et de quantifier les erreurs d’estimation pour de telles données. Ce travail de thèse a ainsi été motivé par un jeu de données d’abondance de poi

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Tieppo, Sandra Maria. "Inferência em um modelo de regressão com resposta binária na presença de sobredispersão e erros de medição." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-26042007-172251/.

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Modelos de regressão com resposta binária são utilizados na solução de problemas nas mais diversas áreas. Neste trabalho enfocamos dois problemas comuns em certos conjuntos de dados e que requerem técnicas apropriadas que forneçam inferências satisfatórias. Primeiro, em certas aplicações uma mesma unidade amostral é utilizada mais de uma vez, acarretando respostas positivamente correlacionadas, responsáveis por uma variância na variável resposta superior ao que comporta a distribuição binomial, fenômeno conhecido como sobredispersão. Por outro lado, também encontramos situações em que a variáv

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Le, Rest Kévin. "Méthodes statistiques pour la modélisation des facteurs influençant la distribution et l’abondance de populations : application aux rapaces diurnes nichant en France." Thesis, Poitiers, 2013. http://www.theses.fr/2013POIT2330/document.

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Face au déclin global de la biodiversité, de nombreux suivis de populations animales et végétales sont réalisés sur de grandes zones géographiques et durant une longue période afin de comprendre les facteurs déterminant la distribution, l’abondance et les tendances des populations. Ces suivis à larges échelles permettent de statuer quantitativement sur l’état des populations et de mettre en place des plans de gestion appropriés en accord avec les échelles biologiques. L’analyse statistique de ce type de données n’est cependant pas sans poser un certain nombre de problèmes. Classiquement, on ut

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Costa, Maria da Conceição Cristo Santos Lopes. "Optimal alarms systems and its application to financial time series." Doctoral thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/12872.

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Doutoramento em Matemática<br>This thesis focuses on the application of optimal alarm systems to non linear time series models. The most common classes of models in the analysis of real-valued and integer-valued time series are described. The construction of optimal alarm systems is covered and its applications explored. Considering models with conditional heteroscedasticity, particular attention is given to the Fractionally Integrated Asymmetric Power ARCH, FIAPARCH(p; d; q) model and an optimal alarm system is implemented, following both classical and Bayesian methodologies. Taking i

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Hammami, Imen. "Statistical properties of parasite density estimators in malaria and field applications." Phd thesis, Université René Descartes - Paris V, 2013. http://tel.archives-ouvertes.fr/tel-01064071.

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Malaria is a devastating global health problem that affected 219 million people and caused 660,000 deaths in 2010. Inaccurate estimation of the level of infection may have adverse clinical and therapeutic implications for patients, and for epidemiological endpoint measurements. The level of infection, expressed as the parasite density (PD), is classically defined as the number of asexual parasites relative to a microliter of blood. Microscopy of Giemsa-stained thick blood smears (TBSs) is the gold standard for parasite enumeration. Parasites are counted in a predetermined number of high-power

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Llorens, Aleixandre Noelia. "Evaluación en el modelado de las respuestas de recuento." Doctoral thesis, Universitat de les Illes Balears, 2005. http://hdl.handle.net/10803/9446.

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Este trabajo presenta dos líneas de investigación desarrolladas en los últimos años en torno a la etapa de evaluación en datos de recuento. Los campos de estudio han sido: los datos de recuento, concretamente el estudio del modelo de regresión de Poisson y sus extensiones y la etapa de evaluación como punto de inflexión en el proceso de modelado estadístico. Los resultados obtenidos ponen de manifiesto la importancia de aplicar el modelo adecuado a las características de los datos así como de evaluar el ajuste del mismo. Por otra parte la comparación de pruebas, índices, estimadores y modelos

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Leask, Kerry Leigh. "Wadley's problem with overdispersion." Thesis, 2009. http://hdl.handle.net/10413/9319.

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Wadley’s problem frequently emerges in dosage-mortality data and is one in which the number of surviving organisms is observed but the number initially treated is unknown. Data in this setting are also often overdispersed, that is the variability within the data exceeds that described by the distribution modelling it. The aim of this thesis is to explore distributions that can accommodate overdispersion in a Wadley’s problem setting. Two methods are essentially considered. The first considers adapting the beta-binomial and multiplicative binomial models that are frequently used for overdispers

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McNeney, W. Brad. "Overdispersion in poisson regression." Thesis, 1992. http://hdl.handle.net/2429/2230.

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Investigation of a possible relationship between air quality and human health in the community of Prince George, British Columbia was undertaken after a public opinion poll in 1972 discovered that poor air quality was the number one concern of the residents of Prince George. An analysis which attempted to identify such relationships using a data set including air quality measurements and hospital admissions for the period April 1, 1984 to March 31, 1986 is discussed in Knight, Leroux, Millar, and Petkau (1988). A similar analysis using emergency room visits during the same period rather than h

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Chan, Chien-Hui, and 詹千慧. "The Tolerance Bounds for Overdispersion Data." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/78626543256575261095.

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Ganio-Gibbons, Lisa M. "Diagnostic tools for overdispersion in generalized linear models." Thesis, 1989. http://hdl.handle.net/1957/38199.

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Data in the form of counts or proportions often exhibit more variability than that predicted by a Poisson or binomial distribution. Many different models have been proposed to account for extra-Poisson or extra-binomial variation. A simple model includes a single heterogeneity factor (dispersion parameter) in the variance. Other models that allow the dispersion parameter to vary between groups or according to a continuous covariate also exist but require a more complicated analysis. This thesis is concerned with (1) understanding the consequences of using an oversimplified model for overdisper

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Chen, Wei-Liang, and 陳維梁. "Component Inference on Mixture Model of Overdispersion Poisson." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/58ed4r.

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碩士<br>國立交通大學<br>統計學研究所<br>107<br>PIN is also known as the probability of informed trading,under which we expect the stock market trading situation to be a mixture of three discrete types following Poisson distributions. If we can decode the groups from the data, we can calculate the PIN.However,by closely examine the data,we found out that the data comes from a mixture of overdispersion Poisson distribution ,which give raise to the need of effectively inference the group from such mixture distribution .After using rebmix, Mclust, flexmix with no effective results, we turn to StepSignalMargiL

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sheng-chu, su, and 蘇聖珠. "A Study of Modelling Categorical Data with Overdispersion or Underdispersion." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/73543733781294593975.

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博士<br>國立政治大學<br>統計學系<br>88<br>This paper presents a modelling method of analyzing categorical data with overdispersion or underdispersion. In many studies, data are collected from differ clusters, and members within the same cluster behave similary. Thus, the responses of members within the same cluster are not independent and the multinomial distribution is not the correct distribution for the observed counts. Therefore, the covariance matrix of the sample proportion vector tends to be much different from that of the multinomial model. We discuss four different models to fit counts data w

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Chen, Pei-Fen, and 陳珮芬. "Research of Modeling Overdispersion for Analyzing Plant Disease Incidence Data." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/17012855561878738978.

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碩士<br>國立中興大學<br>農藝學系所<br>94<br>Incidence data tend to be clustered or aggregated in plant epidemiology. The data with cluster exhibit overdispersion, a phenomenon known as heterogeneity when the statistical analysis is going on. Overdispersion means that the actual variance of the interested parameter exceeds the expected variance. It leads to the incorrect estimate of standard error for the interested parameter. Thus, the final conclusion is often misled. Recently, there have existed a lot literatures discussing overdispersion phenomenon in the plant epidemiology, for example: Beta-binomial m

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Guo, Ding-shiuan, and 郭定璿. "On the Adjustment of the Overdispersion in Property Insurance Data." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/52740419728549129999.

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碩士<br>國立高雄第一科技大學<br>風險管理與保險研究所<br>101<br>Poisson regression model is widely used in insurance ratemaking, and negative binomial regression model will be applied when the data appear to be over-dispersed. However, it is also possible that the claim numbers may be zero-inflated, and the negative binomial regression is not suitable for those data. 　　Therefore, this research uses the zero-inflated negative binomial model to fit the number of insurance claims. It not only retains the advantages which the negative binomial model can solve for overdispersion, but also improve the phenomenon which its

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Tsao, Ya-ting, and 曹雅婷. "Inference for overdispersion in count data without making distributional assumptions." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/81443827923072996565.

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碩士<br>國立中央大學<br>統計研究所<br>99<br>This thesis provides a method for estimating the over-dispersion count data. And this method adopts the poisson distribution as the working model. The violation of the Bartlett’s second identity is then made use of to give rise to a useful formula for the estimation of the over-dispersion. This new means is applicable for any sensible link function that relates the response probabilities to the variates.

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Lee, Hung, and 李泓. "Control Charts for integer-valued time series models with overdispersion." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/59163690533343244151.

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碩士<br>國立中山大學<br>應用數學系研究所<br>101<br>In this study we consider the integer-valued autoregressive (INAR) model with lognormal innovations which leads to overdispersion property. Freeland and McCabe (2004) derived the score function, the information matrix and new types of residuals for the INAR(1) model with Poisson innovations. In this study, we extend their results to INAR(1) model with lognormal innovations. Cumulative sum (CUSUM) control chart for monitoring the mean and the variance shift of the INAR(1) model with lognormal innovations are proposed.

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Kuo, Li-Yen, and 郭立言. "Alleviation of Data Overdispersion On Implicit Feedback for Recommender Systems." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/q8tb9p.

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博士<br>國立臺灣大學<br>電機工程學研究所<br>107<br>Matrix factorization has earned great success on recommender systems. In real-world implicit feedback, values of entries follow power-law distributions approximately. More specifically, several entries have extraordinary high values, which are called overdispersed ones in this dissertation. The common-used regression-based matrix factorization not only is sensitive to overdispersed data but also unable to guarantee that the predicted values are coordinate with the user preference orders. In light of this, we propose two perspectives for the alleviation of the

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Tsai, Pei-Hsun, and 蔡沛洵. "A study on the integer-valued time series models with overdispersion." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/05765042285169986771.

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碩士<br>國立中山大學<br>應用數學系研究所<br>101<br>Time series of counts observed in practice often exhibit overdispersion. The integer-valued generalized autoregressive conditional heteroscedastic (Ingarch) models are commonly used for count time series with overdispersion. We assume the conditional mean of an Ingarch model follows a Poisson distribution or other distributions, such as the negative Binomial distribution or the Generalized Poisson distribution. In this study, we investigate the properties, estimation of these Ingarch models. Two estimation methods: conditional least squares and maximum likel

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Hsu, Yu-Ting, and 徐郁婷. "Comparing the Generalized Poisson Regression And Negative Binomial Regression Methods In Dealing With Overdispersion." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/y8n823.

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碩士<br>國立陽明大學<br>公共衛生研究所<br>105<br>Understand the characteristics of infectious diseases, contribute to the assessment of the disease epidemic, the future development trend for further study, and health policy makers to take appropriate health policy to prevent the expansion of the disease. Dengue fever is the main exploratory infectious diseases in this research. The number of cases of dengue fever was treated as response variables, which was a discrete type and the number of morbidity was not large. The Poisson regression model, which is a common type of discrete data, was selected as a bench

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Godwin, Ryan T. "Econometric analysis of non-standard count data." Thesis, 2012. http://hdl.handle.net/1828/4315.

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This thesis discusses various issues in the estimation of models for count data. In the first part of the thesis, we derive an analytic expression for the bias of the maximum likelihood estimator (MLE) of the parameter in a doubly-truncated Poisson distribution, which proves highly effective as a means of bias correction. We explore the circumstances under which bias is likely to be problematic, and provide some indication of the statistical significance of the bias. Over a range of sample sizes, our method outperforms the alternative of bias correction via the parametric bootstrap. We show th

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Škoda, Štěpán. "Modelování četností pojistných událostí." Master's thesis, 2013. http://www.nusl.cz/ntk/nusl-328285.

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1 Abstract: The present work investigates techniques of insurence ratemaking accor- ding to the claims counts of policyholders on the basis of information contained in policies. At the beginning, we provide a closer examination of the theory of genera- lized linear models, which have wide range of applications in the field of actuarial modeling. The second chapter presents the basic Poisson regression model as well as some particular verification methods. Specifically, deviance and Wald test could be found here and furthermore also important results for residuals. The third chapter contains in

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"Statistical validation of limiting similarity and negative co-occurrence null models : Extending the models to gain insights into sub-community patterns of community assembly." Thesis, 2014. http://hdl.handle.net/10388/ETD-2014-09-1715.

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Competition between species is believed to lead to patterns of either competitive exclusion or limiting similarity within ecological communities; however, to date the amount of support for either as an outcome has been relatively weak. The two classes of null model commonly used to assess co-occurrence and limiting similarity have both been well studied for statistical performance; however, the methods used to evaluate their performance, particularly in terms of type II statistical errors, may have resulted in the underreporting of both patterns in the communities tested. The overall purpose o

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Paulo, Domingos Gonçalves. "Modelo de egressão de Poisson Generalizado: análise de dados de contagem com sobredispersão e subdispersão." Master's thesis, 2019. http://hdl.handle.net/1822/65273.

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Dissertação de mestrado em Estatística<br>A distribuição de Poisson é uma referência para os modelos de regressão para dados de contagem. No entanto, a restrição de equidispersão, isto é, o valor esperado e a variância condicionais são iguais, não representa com precisão os dados reais. De facto, existem muitas situações, onde os dados de contagem apresentam sobredispersão ou subdispersão e na modelação deste tipo de dados, a aplicação do modelo de regressão de Poisson revela-se inadequada, uma vez que pode originar a subestimação da variância dos parâmetros. Alguns autores têm desenvolv

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Sebatjane, Phuti. "Understanding patterns of aggregation in count data." Diss., 2016. http://hdl.handle.net/10500/22067.

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The term aggregation refers to overdispersion and both are used interchangeably in this thesis. In addressing the problem of prevalence of infectious parasite species faced by most rural livestock farmers, we model the distribution of faecal egg counts of 15 parasite species (13 internal parasites and 2 ticks) common in sheep and goats. Aggregation and excess zeroes is addressed through the use of generalised linear models. The abundance of each species was modelled using six different distributions: the Poisson, negative binomial (NB), zero-inflated Poisson (ZIP), zero-inflated negative binom

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