Journal articles: 'Command Estimate'

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Wang, Zhiqiang. "Two Postestimation Commands for Assessing Confounding Effects in Epidemiological Studies." Stata Journal: Promoting communications on statistics and Stata 7, no. 2 (June 2007): 183–96. http://dx.doi.org/10.1177/1536867x0700700203.

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Confounding is a major issue in observational epidemiological studies. This paper describes two postestimation commands for assessing confounding effects. One command (confall) displays and plots all possible effect estimates against one of p-value, Akaike information criterion, or Bayesian information criterion. This computing-intensive procedure allows researchers to inspect the variability of the effect estimates from various possible models. Another command (chest) uses a stepwise approach to identify variables that have substantially changed the effect estimate. Both commands can be used after most common estimation commands in epidemiological studies, such as logistic regression, conditional logistic regression, Poisson regression, linear regression, and Cox proportional hazards models.

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Jung, Yoo Sun, Flávio D. S. Souza, Andrew Q. Philips, Amanda Rutherford, and Guy D. Whitten. "A command to estimate and interpret models of dynamic compositional dependent variables: New features for dynsimpie." Stata Journal: Promoting communications on statistics and Stata 20, no. 3 (September 2020): 584–603. http://dx.doi.org/10.1177/1536867x20953570.

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Philips, Rutherford, and Whitten (2016, Stata Journal 16: 662–677) introduced dynsimpie, a command to examine dynamic compositional dependent variables. In this article, we present an update to dynsimpie and three new adofiles: cfbplot, effectsplot, and dynsimpiecoef. These updates greatly enhance the range of models that can be estimated and the ways in which model results can now be presented. The command dynsimpie has been updated so that users can obtain both prediction plots and change-from-baseline plots using postestimation commands. With the new command dynsimpiecoef, various types of coefficient plots can also be obtained. We illustrate these improvements using monthly data on support for political parties in the United Kingdom.

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Ruhe, Constantin. "Bootstrap pointwise confidence intervals for covariate-adjusted survivor functions in the Cox model." Stata Journal: Promoting communications on statistics and Stata 19, no. 1 (March 2019): 185–99. http://dx.doi.org/10.1177/1536867x19830915.

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Survival functions are a common visualization of predictions from the Cox model. However, neither Stata’s stcurve command nor the communitycontributed scurve tvc command allows one to estimate confidence intervals. In this article, I discuss how bootstrap confidence intervals can be formed for covariate-adjusted survival functions in the Cox model. The new bsurvci command automates this procedure and allows users to visualize the results. bsurvci enables one to estimate uncertainty around survival functions estimated from Cox models with time-varying coefficients, a capability that was not previously available in Stata. Furthermore, it provides Stata users with an additional option for survival estimates from Cox models with proportional hazards by allowing them to choose between bootstrap confidence intervals using bsurvci and asymptotic confidence intervals from an existing community-contributed command, survci. Because asymptotic confidence intervals make distributional assumptions when constructing confidence intervals, the bootstrap procedure proposed in this article provides a nonparametric alternative.

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Bottai, Matteo, and Nicola Orsini. "qmodel: A command for fitting parametric quantile models." Stata Journal: Promoting communications on statistics and Stata 19, no. 2 (June 2019): 261–93. http://dx.doi.org/10.1177/1536867x19854002.

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In this article, we introduce the qmodel command, which fits parametric models for the conditional quantile function of an outcome variable given covariates. Ordinary quantile regression, implemented in the qreg command, is a popular, simple type of parametric quantile model. It is widely used but known to yield erratic estimates that often lead to uncertain inferences. Parametric quantile models overcome these limitations and extend modeling of conditional quantile functions beyond ordinary quantile regression. These models are flexible and efficient. qmodel can estimate virtually any possible linear or nonlinear parametric model because it allows the user to specify any combination of qmodel-specific built-in functions, standard mathematical and statistical functions, and substitutable expressions. We illustrate the potential of parametric quantile models and the use of the qmodel command and its postestimation commands through realand simulated-data examples that commonly arise in epidemiological and pharmacological research. In addition, this article may give insight into the close connection that exists between quantile functions and the true mathematical laws that generate data.

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Rios-Avila, Fernando. "Estimation of marginal effects for models with alternative variable transformations." Stata Journal: Promoting communications on statistics and Stata 21, no. 1 (March 2021): 81–96. http://dx.doi.org/10.1177/1536867x211000005.

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margins is a powerful postestimation command that allows the estimation of marginal effects for official and community-contributed commands, with well-defined predicted outcomes (see predict). While the use of factor-variable notation allows one to easily estimate marginal effects when interactions and polynomials are used, estimation of marginal effects when other types of transformations such as splines, logs, or fractional polynomials are used remains a challenge. In this article, I describe how margins‘s capabilities can be extended to analyze other variable transformations using the command f_able.

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Castronovo, Anna Margherita, Cristiano De Marchis, Maurizio Schmid, Silvia Conforto, and Giacomo Severini. "Effect of Task Failure on Intermuscular Coherence Measures in Synergistic Muscles." Applied Bionics and Biomechanics 2018 (June 3, 2018): 1–13. http://dx.doi.org/10.1155/2018/4759232.

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The term “task failure” describes the point when a person is not able to maintain the level of force required by a task. As task failure approaches, the corticospinal command to the muscles increases to maintain the required level of force in the face of a decreased mechanical efficacy. Nevertheless, most motor tasks require the synergistic recruitment of several muscles. How this recruitment is affected by approaching task failure is still not clear. The increase in the corticospinal drive could be due to an increase in synergistic recruitment or to overlapping commands sent to the muscles individually. Herein, we investigated these possibilities by combining intermuscular coherence and synergy analysis on signals recorded from three muscles of the quadriceps during dynamic leg extension tasks. We employed muscle synergy analysis to investigate changes in the coactivation of the muscles. Three different measures of coherence were used. Pooled coherence was used to estimate the command synchronous to all three muscles, pairwise coherence the command shared across muscle pairs and residual coherence the command peculiar to each couple of muscles. Our analysis highlights an overall decrease in synergistic command at task failure and an intensification of the contribution of the nonsynergistic shared command.

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Manjón, Miguel, and Juan Mañez. "Production Function Estimation in Stata Using the Ackerberg–Caves–Frazer Method." Stata Journal: Promoting communications on statistics and Stata 16, no. 4 (December 2016): 900–916. http://dx.doi.org/10.1177/1536867x1601600406.

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We present a new e-class command, acfest, that implements the method of Ackerberg, Caves, and Frazer (2015, Econometrica 83: 2411–2451) to estimate production functions. This method deals with the functional dependence problems that may arise in the methods proposed by Olley and Pakes (1996, Econometrica 64: 1263–1297) and, particularly, Levinsohn and Petrin (2003, Review of Economic Studies 70: 317–341) (implemented in Stata by Yasar, Raciborski, and Poi [2008, Stata Journal 8: 221–231] and Petrin, Poi, and Levinsohn [2004, Stata Journal 4: 113–123], respectively). In particular, the acfest command yields (nonlinear, robust) generalized method of moments estimates using a Mata function and two specification tests (Wald and Sargan–Hansen). After estimation, predict provides the estimated productivity of the firms in the sample.

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Brown, Graham K., and Thanos Mergoupis. "Treatment Interactions with Nonexperimental Data in Stata." Stata Journal: Promoting communications on statistics and Stata 11, no. 4 (December 2011): 545–55. http://dx.doi.org/10.1177/1536867x1201100403.

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Treatment effects may vary with the observed characteristics of the treated, often with important implications. In the context of experimental data, a growing literature deals with the problem of specifying treatment interaction terms that most effectively capture this variation. Some results of this literature are now implemented in Stata. With nonexperimental (observational) data, and in particular when selection into treatment depends on unmeasured factors, treatment effects can be estimated using Stata's treatreg command. Though not originally designed for this purpose, treatreg can be used to consistently estimate treatment interaction parameters. With interactions, however, adjustments are required to generate predicted values and estimate the average treatment effect. In this article, we introduce commands that perform this adjustment for multiplicative interactions, and we show the required adjustment for more complicated interactions.

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Fé, Eduardo, and Richard Hofler. "sfcount: Command for count-data stochastic frontiers and underreported and overreported counts." Stata Journal: Promoting communications on statistics and Stata 20, no. 3 (September 2020): 532–47. http://dx.doi.org/10.1177/1536867x20953566.

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In this article, we introduce a new command, sfcount, to fit count-data stochastic frontier models. Although originally designed to estimate production and production-cost functions, this new command can be used to estimate mean regression functions when count data are suspected to be underreported or over-reported.

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Sun, Yutao, and Geert Dhaene. "xtspj: A command for split-panel jackknife estimation." Stata Journal: Promoting communications on statistics and Stata 19, no. 2 (June 2019): 335–74. http://dx.doi.org/10.1177/1536867x19854016.

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In this article, we present a new command, xtspj, that corrects for incidental parameter bias in panel-data models with fixed effects. The correction removes the first-order bias term of the maximum likelihood estimate using the split-panel jackknife method. Two variants are implemented: the jackknifed maximum-likelihood estimate and the jackknifed log-likelihood function (with corresponding maximizer). The model may be nonlinear or dynamic, and the covariates may be predetermined instead of strictly exogenous. xtspj implements the split-panel jackknife for fixed-effects versions of linear, probit, logit, Poisson, exponential, gamma, Weibull, and negbin2 regressions. It also accommodates other models if the user specifies the log-likelihood function (and, possibly but not necessarily, the score function and the Hessian). xtspj is fast and memory efficient, and it allows large datasets. The data may be unbalanced. xtspj can also be used to compute uncorrected maximum-likelihood estimates of fixed-effects models for which no other xt (see [XT] xt) command exists.

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Bower, Hannah, Michael J. Crowther, and Paul C. Lambert. "Strcs: A Command for Fitting Flexible Parametric Survival Models on the Log-hazard Scale." Stata Journal: Promoting communications on statistics and Stata 16, no. 4 (December 2016): 989–1012. http://dx.doi.org/10.1177/1536867x1601600410.

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In this article, we describe strcs, a user-written command for fitting flexible parametric survival models on the log-hazard scale. strcs is an extension of the user-written stgenreg command (Crowther and Lambert, 2013b, Journal of Statistical Software 53(12): 1–17), which fits general parametric models with user-defined hazard functions using numerical integration. strcs implements a two-step method that incorporates both analytical and numerical integration to estimate the cumulative hazard function required for the log-likelihood function. This method improves the accuracy of the fully numeric estimation implemented in stgenreg. Time-dependent effects can be incorporated, and excess mortality models can be fit by using the available options. We also describe some of the extensive postestimation commands that are easily implemented after fitting an strcs model.

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Daza, Eric J., Michael G. Hudgens, and Amy H. Herring. "Estimating Inverse-probability Weights for Longitudinal Data with Dropout or Truncation: The Xtrccipw Command." Stata Journal: Promoting communications on statistics and Stata 17, no. 2 (June 2017): 253–78. http://dx.doi.org/10.1177/1536867x1701700202.

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Individuals may drop out of a longitudinal study, rendering their outcomes unobserved but still well defined. However, they may also undergo truncation (for example, death), beyond which their outcomes are no longer meaningful. Kurland and Heagerty (2005, Biostatistics 6: 241–258) developed a method to conduct regression conditioning on nontruncation, that is, regression conditioning on continuation (RCC), for longitudinal outcomes that are monotonically missing at random (for example, because of dropout). This method first estimates the probability of dropout among continuing individuals to construct inverse-probability weights (IPWs), then fits generalized estimating equations (GEE) with these IPWs. In this article, we present the xtrccipw command, which can both estimate the IPWs required by RCC and then use these IPWs in a GEE estimator by calling the glm command from within xtrccipw. In the absence of truncation, the xtrccipw command can also be used to run a weighted GEE analysis. We demonstrate the xtrccipw command by analyzing an example dataset and the original Kurland and Heagerty (2005) data. We also use xtrccipw to illustrate some empirical properties of RCC through a simulation study.

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Hyer, Eric. "China's Arms Merchants: Profits in Command." China Quarterly 132 (December 1992): 1101–18. http://dx.doi.org/10.1017/s0305741000045550.

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Since the founding of the People's Republic of China, Beijing has engaged in foreign arms transfers. Transfers during the early period went almost unnoticed because they were on a very small scale, were almost invariably gratis, and had little or no impact on the world's arms trade. This low profile changed during the 1980s as China became one of the world's major arms dealers. Beijing estimates that income from arms exports is about US$1.34 billion annually, but other sources estimate that it is over US$2 billion. This dramatic increase attracted attention in October 1987 when Chinese Silkworm missiles fired from Iran badly damaged oil tankers in the Persian Gulf, including American-reflagged Kuwaiti tankers. Only then did the international community recognize that China had become a major arms supplier to the Third World.

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Hasebe, Takuya. "Endogenous switching regression model and treatment effects of count-data outcome." Stata Journal: Promoting communications on statistics and Stata 20, no. 3 (September 2020): 627–46. http://dx.doi.org/10.1177/1536867x20953573.

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In this article, I describe the escount command, which implements the estimation of an endogenous switching model with count-data outcomes, where a potential outcome differs across two alternate treatment statuses. escount allows for either a Poisson or a negative binomial regression model with lognormal latent heterogeneity. After estimating the parameters of the switching regression model, one can estimate various treatment effects with the command teescount. I also describe the command lncount, which fits the Poisson or negative binomial regression model with lognormal latent heterogeneity.

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Lambert, Paul C. "The Estimation and Modeling of Cause-specific Cumulative Incidence Functions Using Time-dependent Weights." Stata Journal: Promoting communications on statistics and Stata 17, no. 1 (March 2017): 181–207. http://dx.doi.org/10.1177/1536867x1701700110.

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Competing risks occur in survival analysis when an individual is at risk of more than one type of event and one event's occurrence precludes another's. The cause-specific cumulative incidence function (CIF) is a measure of interest with competing-risks data. It gives the absolute (or crude) risk of having the event by time t, accounting for the fact that it is impossible to have the event if a competing event occurs first. The user-written command stcompet calculates nonparametric estimates of the cause-specific CIF, and the official Stata command stcrreg fits the Fine and Gray (1999, Journal of the American Statistical Association 94: 496–509) model for competing-risks data. Geskus (2011, Biometrics 67: 39–49) has recently shown that standard software can estimate some of the key measures in competing risks by restructuring the data and incorporating weights. This has a number of advantages because any tools developed for standard survival analysis can then be used to analyze competing-risks data. In this article, I describe the stcrprep command, which restructures the data and calculates the appropriate weights. After one uses stcrprep, a number of standard Stata survival analysis commands can then be used to analyze competing risks. For example, sts graph, failure will give a plot of the cause-specific CIF, and stcox will fit the Fine and Gray (1999) proportional subhazards model. Using stcrprep together with stcox is computationally much more efficient than using stcrreg. In addition, stcrprep opens up new opportunities for competing-risk models. I illustrate this by fitting flexible parametric survival models to the expanded data to directly model the cause-specific CIF.

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Fagergren, Anders, Örjan Ekeberg, and Hans Forssberg. "Control Strategies Correcting Inaccurately Programmed Fingertip Forces: Model Predictions Derived From Human Behavior." Journal of Neurophysiology 89, no. 6 (June 2003): 2904–16. http://dx.doi.org/10.1152/jn.00939.2002.

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When picking up a familiar object between the index finger and the thumb, the motor commands are predetermined by the CNS to correspond to the frictional demand of the finger-object contact area. If the friction is less than expected, the object will start to slip out of the hand, giving rise to unexpected sensory information. Here we study the correction strategies of the motor system in response to an unexpected frictional demand. The motor commands to the mononeuron pool are estimated by a novel technique combining behavioral recordings and neuromuscular modelling. We first propose a mathematical model incorporating muscles, hand mechanics, and the action of lifting an object. A simple control system sends motor commands to and receives sensory signals from the model. We identify three factors influencing the efficiency of the correction: the time development of the motor command, the delay between the onset of the grip and load forces (GF-LF-delay), and how fast the lift is performed. A sensitivity analysis describes how these factors affect the ability to prevent or stop slipping and suggests an efficient control strategy that prepares and corrects for an altered frictional condition. We then analyzed fingertip grip and load forces (GF and LF) and position data from 200 lifts made by five healthy subjects. The friction was occasionally reduced, forcing an increase of the GF to prevent the object being dropped. The data were then analyzed by feeding it through the inverted model. This provided an estimate of the motor commands to the motoneuron pool. As suggested by the sensitivity analysis the GF-LF-delay was indeed used by the subjects to prevent slip. In agreement with recordings from neurons in the primary motor cortex of the monkey, a sharp burst in the estimated GF motor command (NGF) efficiently arrested any slip. The estimated motor commands indicate a control system that uses a small set of corrective commands, which together with the GF-LF-delay form efficient correction strategies. The selection of a strategy depends on the amount of tactile information reporting unexpected friction and how long it takes to arrive. We believe that this technique of estimating the motor commands behind the fingertip forces during a precision grip lift can provide a powerful tool for the investigation of the central control of the motor system.

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Varadarajan, N., and B. K. Purandara. "SaltMod estimation of root-zone salinity Varadarajan and Purandara Application of SaltMod to estimate root-zone salinity in a command area." Materials and Geoenvironment 65, no. 2 (September 1, 2018): 79–88. http://dx.doi.org/10.2478/rmzmag-2018-0008.

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Abstract Waterlogging and salinity are the common features associated with many of the irrigation commands of surface water projects. This study aims to estimate the root zone salinity of the left and right bank canal commands of Ghataprabha irrigation command, Karnataka, India. The hydro-salinity model SaltMod was applied to selected agriculture plots at Gokak, Mudhol, Biligi and Bagalkot taluks for the prediction of root-zone salinity and leaching efficiency. The model simulated the soil-profile salinity for 20 years with and without subsurface drainage. The salinity level shows a decline with an increase of leaching efficiency. The leaching efficiency of 0.2 shows the best match with the actual efficiency under adequate drainage conditions. The model shows a steady increase, reaching the levels up to 8.0 decisiemens/metre (dS/m) to 10.6 dS/m at the end of the 20-year period under no drainage. If suitable drainage system is not provided, the area will further get salinised, thus making the land uncultivable. We conclude from the present study that it is necessary to provide proper drainage facilities to control the salinity levels in the study area.

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Sterne, Jonathan A. C., and Kate Tilling. "G-estimation of Causal Effects, Allowing for Time-varying Confounding." Stata Journal: Promoting communications on statistics and Stata 2, no. 2 (June 2002): 164–82. http://dx.doi.org/10.1177/1536867x0200200205.

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This article describes the stgest command, which implements G-estimation (as proposed by Robins) to estimate the effect of a time-varying exposure on survival time, allowing for time-varying confounders.

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Turovskiy, Ya A., A. V. Mamaev, A. V. Alekseev, and S. V. Borzunov. "Subjective time scales when working with perspective human-computer interfaces." Experimental Psychology (Russia) 12, no. 2 (2019): 75–86. http://dx.doi.org/10.17759/exppsy.2019120206.

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The analysis of subjective time scales of the subjects with perspective human-computer interfaces was carried out: neurocomputer (brain-computer), electromyographic, oculografic. It is shown that for all of them it is typical to underestimate the maximum time spent for the execution of one team. In this case, for the electromyographic and oculografic, this feature is also preserved for the indicators of the average time for executing the commands. The results of the assessment demonstrate a unified approach of users to the formation of subjective time when working with various interfaces: the user estimates both the averaged and the best (minimum) with the worst (maximum) time for executing commands on a single scale. Subjects who switched worse from generating one command for the interface to another subjectively rated the interface as slower. The HRV data showed the LF-band relationship with a subjective estimate of the time spent working with the interface. Analysis of the relationship (true time-subjective) / true time has shown that subjective time scales when working with the neurocomputer and oculographic interfaces demonstrate a high correlation with each other as opposed to electromyographic.

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Kartal, Sinan. "Forecasting future performance of irrigation schemes: The case of Bergama." Turkish Journal of Agriculture - Food Science and Technology 9, no. 4 (April 25, 2021): 769–74. http://dx.doi.org/10.24925/turjaf.v9i4.769-774.4184.

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Potential outputs of irrigation should be put forth to improve the yields in agricultural practices. Available water resources should efficiently be used to improve yields and inputs should be minimized. Performance assessment of irrigation schemes is an importance issue for improved yields and to take relevant measured. Statistical methods are used for performance assessment of irrigation schemes with the use of various indicators. Forecasts for future performance of irrigation shames will facilitate the steps to be taken by decision-makers to improve performance. In this study, time series – ARIMA method was used to forecast future performance of Bergama irrigation scheme for 2017-2021 period. The indicator values of annual irrigation water supply per unit command area, output per unit command area and total expenditure per unit command area for 2006-2017 period were used to estimate performance indicators for 2017-2021 period. In 2021, at 95% probability, the lowest annual irrigation water supply per unit-command area was calculated as 4365.10 m3 ha-1 and the highest as 16835.69 m3 ha-1; the lowest output per unit command area was calculated as -5076.10 € ha-1 and the highest as 10401.2 € ha-1; the lowest total expenditure per unit command area was calculated as -2200.41 € ha-1 and the highest as 1866.31 € ha-1. Present forecasts of time series -ARIMA method with the use of data of 2006-2016 period revealed that annual irrigation water supply per unit-command area and output per unit command area will increase and total expenditure per unit command area will decrease in years.

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Li, Jia, Zhipeng Liao, and Mengsi Gao. "Uniform nonparametric inference for time series using Stata." Stata Journal: Promoting communications on statistics and Stata 20, no. 3 (September 2020): 706–20. http://dx.doi.org/10.1177/1536867x20953576.

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In this article, we introduce a command, tssreg, that conducts nonparametric series estimation and uniform inference for time-series data, including the case with independent data as a special case. This command can be used to nonparametrically estimate the conditional expectation function and the uniform confidence band at a user-specified confidence level, based on an econometric theory that accommodates general time-series dependence. The uniform inference tool can also be used to perform nonparametric specification tests for conditional moment restrictions commonly seen in dynamic equilibrium models.

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D’Haultfœuille, Xavier, Lucas Girard, and Roland Rathelot. "segregsmall: A command to estimate segregation in the presence of small units." Stata Journal: Promoting communications on statistics and Stata 21, no. 1 (March 2021): 152–79. http://dx.doi.org/10.1177/1536867x211000018.

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Suppose that a population, composed of a minority and a majority group, is allocated into units, which can be neighborhoods, firms, classrooms, etc. Qualitatively, there is some segregation whenever allocation leads to the concentration of minority individuals in some units more than in others. Quantitative measures of segregation have struggled with the small-unit bias. When units contain few individuals, indices based on the minority shares in units are upward biased. For instance, they would point to a positive amount of segregation even when allocation is strictly random. The command segregsmall implements three recent methods correcting for such bias: the nonparametric, partial identification approach of D’Haultfœuille and Rathelot (2017, Quantitative Economics 8: 39–73); the parametric model of Rathelot (2012, Journal of Business & Economic Statistics 30: 546–553); and the linear correction of Carrington and Troske (1997, Journal of Business & Economic Statistics 15: 402–409). The package also allows for conditional analyses, namely, measures of segregation accounting for characteristics of the individuals or the units.

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Alejo, Javier, Antonio F. Galvao, and Gabriel Montes-Rojas. "A practical generalized propensity-score estimator for quantile continuous treatment effects." Stata Journal: Promoting communications on statistics and Stata 20, no. 2 (June 2020): 276–96. http://dx.doi.org/10.1177/1536867x20930997.

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In this article, we present a new command, qcte, that implements several methods for estimation and inference for quantile treatment-effects models with a continuous treatment. We propose a semiparametric two-step estimator, where the first step is based on a flexible Box–Cox model, as the default model of the command. We develop practical statistical inference procedures using bootstrap. We implement some simulations to show that the proposed methods perform well. Finally, we apply qcte to a survey of Massachusetts lottery winners to estimate the unconditional quantile effects of the prize amount, as a proxy of nonlabor income changes, on subsequent labor earnings from U.S. Social Security records. The empirical results reveal strong heterogeneity across unconditional quantiles.

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Chen, Feng, Guangjun He, and Qifang He. "A finite-time-convergent composite guidance law with strong fault-tolerant performance." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 9 (August 24, 2018): 3120–30. http://dx.doi.org/10.1177/0954410018793280.

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To improve the performance of tracking and intercepting the low-altitude target, a nonlinear integral sliding mode guidance law is designed firstly, which can guarantee that the line-of-sight angle converges to a desired tracking angle and the line-of-sight angular rate converges to zero in finite time. Meanwhile, to solve the chattering problem caused by the high gain coefficient of the sign function in the guidance law, a sliding mode disturbance observer is designed to estimate the maneuvering acceleration of the target. Moreover, a composite nonlinear integral sliding mode guidance law is designed by introducing the estimated value of the acceleration, which can weaken the chattering phenomenon effectively. Finally, considering the magnitude loss fault of the guidance command that may occur in the practical implementation, a composite guidance law with strong fault-tolerant performance is designed by introducing a fault compensation command, which can effectively improve the reliability of the system.

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Waseem, H., S. Shahbaz, and J. Razzak. "(A154) Overcrowding of Ambulances at the Scene of a Disaster: Pitfalls and Implications." Prehospital and Disaster Medicine 26, S1 (May 2011): s53. http://dx.doi.org/10.1017/s1049023x11001713.

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IntroductionPakistan is a developing country with a basic prehospital system in some cities. The prehospital services are a mixture of government and private ambulances.There is no central regulatory body for them and no central command to control the influx and out flux of ambulances from the scene.ObjectiveIn this paper, five episodes of terrorist incidents in the country and will try to estimate the number of ambulances on the scene.MethodsRetrospective data was collected and triangulation was done by three sources: (1) ambulance records; (2) visual estimation; and (3) print media. An estimate of total ambulances was reached along with dead and injured. Furthermore medical transport capacity was calculated where possible.ResultsIn majority of the incidents, it was found that there was a huge influx of ambulances beyond the need. This further adds to the chaos and confusion already present on the scene of disaster.ConclusionsA Command and Control Center should be established to direct all ambulance control and movements.

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Liwiński, Jacek. "The wage premium from foreign language skills." Empirica 46, no. 4 (September 21, 2019): 691–711. http://dx.doi.org/10.1007/s10663-019-09459-0.

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Abstract The globalisation of labour markets makes language skills one of the key competences required by employers nowadays. The purpose of this paper is to estimate the wage premium from the foreign language skills earned by Poles. Poles seem to be a good case study, because the Polish language is not used for international communication and as many as 58% of Poles command at least one foreign language. I use data from three waves (2012–2014) of the Human Capital Balance survey with a pooled sample of about 35,000 individuals. I estimate a wage equation with the Heckman correction for selection to employment and I check for robustness with propensity score matching. I find that the advanced command of a foreign language yields a wage premium of 11% on average. Interestingly, I find a much higher wage premium from proficiency in Spanish (32%), French (22%) or Italian (15%) than from proficiency in English (11%) or German (12%).

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Dean, Paul, John Porrill, and Paul A. Warren. "Optimality of Position Commands to Horizontal Eye Muscles: A Test of the Minimum-Norm Rule." Journal of Neurophysiology 81, no. 2 (February 1, 1999): 735–57. http://dx.doi.org/10.1152/jn.1999.81.2.735.

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Optimality of position commands to horizontal eye muscles: a test of the minimum-norm rule. Six muscles control the position of the eye, which has three degrees of freedom. Daunicht proposed an optimization rule for solving this redundancy problem, whereby small changes in eye position are maintained by the minimum possible change in motor commands to the eye (the minimum-norm rule). The present study sought to test this proposal for the simplified one-dimensional case of small changes in conjugate eye position in the horizontal plane. Assuming such changes involve only the horizontal recti, Daunicht’s hypothesis predicts reciprocal innervation with the size of the change in command matched to the strength of the recipient muscle at every starting position of the eye. If the motor command to a muscle is interpreted as the summed firing rate of its oculomotor neuron (OMN) pool, the minimum-norm prediction can be tested by comparing OMN firing rates with forces in the horizontal recti. The comparison showed 1) for the OMN firing rates given by Van Gisbergen and Van Opstal and the muscle forces given by Robinson, there was good agreement between the minimum-norm prediction and experimental observation over about a ±30° range of eye positions. This fit was robust with respect to variations in muscle stiffness and in methods of calculating muscle innervation. 2) Other data sets gave different estimates for the range of eye-positions within which the minimum-norm prediction held. The main sources of variation appeared to be disagreement about the proportion of OMNs with very low firing-rate thresholds (i.e., less than ∼35° in the off direction) and uncertainty about eye-muscle behavior for extreme (>30°) positions of the eye. 3) For all data sets, the range of eye positions over which the minimum-norm rule applied was determined by the pattern of motor-unit recruitment inferred for those data. It corresponded to the range of eye positions over which the size principle of recruitment was obeyed by both agonist and antagonist muscles. It is argued that the current best estimate of the oculomotor range over which minimum-norm control could be used for conjugate horizontal eye position is approximately ±30°. The uncertainty associated with this estimate would be reduced by obtaining unbiased samples of OMN firing rates. Minimum-norm control may result from reduction of the image movement produced by noise in OMN firing rates.

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Bertanha, Marinho, Andrew H. McCallum, Alexis Payne, and Nathan Seegert. "Bunching Estimation of Elasticities Using Stata." Finance and Economics Discussion Series 2021, no. 004 (January 29, 2021): 1–21. http://dx.doi.org/10.17016/feds.2021.006.

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A continuous distribution of agents that face a piecewise-linear schedule of incentives results in a distribution of responses with mass points located where the slope (kink) or intercept (notch) of the schedule changes. Bunching methods use these mass points to estimate an elasticity parameter, which summarizes agents' responses to incentives. This article introduces the command bunching, which implements new non-parametric and semi-parametric identification methods for estimating elasticities developed by Bertanha et al. (2021). These methods rely on weaker assumptions than currently made in the literature and result in meaningfully different estimates of the elasticity in various contexts.

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Jeong, Horyeong, Jong Hyuk Choi, and Jae Suk Lee. "A Current Control Algorithm to Improve Command Tracking Performance and Resilience of a Grid-Connected Inverter." Applied Sciences 10, no. 23 (December 3, 2020): 8642. http://dx.doi.org/10.3390/app10238642.

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This paper presents a stationary reference frame grid current control algorithm for a grid-connected inverter (GCI) to improve command tracking performance and resilience in response to disturbances, i.e., a grid voltage incident in a GCI current control system. In the proposed algorithm, disturbance rejection is applied to reduce the overcurrent at the GCI in response to a grid fault. Disturbances to the GCI current control system are estimated using a grid current observer, and the estimate applied to the grid current controller to activate the disturbance rejection. The stationary reference frame current of a GCI system is also controlled to avoid cross-coupling issues at a synchronous reference frame model, reference transformation and dependency to phase locked loop (PLL) performance. However, the phase lead or lag and steady-state response error, which are drawbacks of AC signal control based on stationary reference frame proportional-integral (PI) controller, must be eliminated in order to secure competition with the synchronous reference PI (SRFPI) controller that was mainly used in the GCI system. Hence, to compensate for command tracking the AC current, such as steady-state response error and phase lead or lag, command feedforward control is applied in the proposed control system. The theory behind the proposed GCI current control algorithm is analyzed, and the proposed algorithm is tested via simulation and experimentation.

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Williams, Richard. "Using the Margins Command to Estimate and Interpret Adjusted Predictions and Marginal Effects." Stata Journal: Promoting communications on statistics and Stata 12, no. 2 (June 2012): 308–31. http://dx.doi.org/10.1177/1536867x1201200209.

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Muniz, Jerônimo Oliveira. "Multistate life tables using Stata." Stata Journal: Promoting communications on statistics and Stata 20, no. 3 (September 2020): 721–45. http://dx.doi.org/10.1177/1536867x20953577.

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The mslt command calculates the functions of a multistate life table and plots a graph of conditional and unconditional life expectancies by time. The command provides linear and exponential solutions to estimate the number of individuals, transitions, probabilities, person-years, and years of life in a given cohort and state of occupancy. The input data are time-specific transition rates (or survivorship proportions) between nonabsorbing and at most one absorbing state. In addition to the mean age at transfer between states, mslt calculates the following summary measures: the mean age, the probability of dying, the average duration, and the proportion of life spent in a specific state.

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Fernandez-Felix, B. M., E. García-Esquinas, A. Muriel, A. Royuela, and J. Zamora. "Bootstrap internal validation command for predictive logistic regression models." Stata Journal: Promoting communications on statistics and Stata 21, no. 2 (June 2021): 498–509. http://dx.doi.org/10.1177/1536867x211025836.

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Overfitting is a common problem in the development of predictive models. It leads to an optimistic estimation of apparent model performance. Internal validation using bootstrapping techniques allows one to quantify the optimism of a predictive model and provide a more realistic estimate of its performance measures. Our objective is to build an easy-to-use command, bsvalidation, aimed to perform a bootstrap internal validation of a logistic regression model.

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Daniel, Rhian M., Bianca L. De Stavola, and Simon N. Cousens. "Gformula: Estimating Causal Effects in the Presence of Time-Varying Confounding or Mediation using the G-Computation Formula." Stata Journal: Promoting communications on statistics and Stata 11, no. 4 (December 2011): 479–517. http://dx.doi.org/10.1177/1536867x1201100401.

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This article describes a new command, gformula, that is an implementation of the g-computation procedure. It is used to estimate the causal effect of time-varying exposures on an outcome in the presence of time-varying confounders that are themselves also affected by the exposures. The procedure also addresses the related problem of estimating direct and indirect effects when the causal effect of the exposures on an outcome is mediated by intermediate variables, and in particular when confounders of the mediator–outcome relationships are themselves affected by the exposures. A brief overview of the theory and a description of the command and its options are given, and illustrations using two simulated examples are provided.

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Greeff, G. P. "Material Flow Rate Estimation in Material Extrusion Additive Manufacturing." NCSL International measure 13, no. 1 (2021): 46–56. http://dx.doi.org/10.51843/measure.13.1.5.

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The additive manufacturing of products promises exciting possibilities. Measurement methodologies, which measure an in-process dataset of these products and interpret the results, are essential. However, before developing such a level of quality assurance several in-process measurands must be realized. One of these is the material flow rate, or rate of adding material during the additive manufacturing process. Yet, measuring this rate directly in material extrusion additive manufacturing presents challenges. This work presents two indirect methods to estimate the volumetric flow rate at the liquefier exit in material extrusion, specifically in Fused Deposition Modeling or Fused Filament Fabrication. The methods are cost effective and may be applied in future sensor integration. The first method is an optical filament feed rate and width measurement and the second is based on the liquefier pressure. Both are used to indirectly estimate the volumetric flow rate. The work also includes a description of linking the G-code command to the final print result, which may be used to create a per extrusion command model of the part.

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Odunga, Pius O., Geoffrey Manyara, and Mark Yobesia. "Estimating the direct contribution of tourism to Rwanda’s economy: Tourism satellite account methodology." Tourism and Hospitality Research 20, no. 3 (July 15, 2019): 259–71. http://dx.doi.org/10.1177/1467358419857786.

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The tourism industry is poised to command a significant role in the economy of Rwanda, a low-income developing country that is rapidly transforming into a service-oriented economy. However, the industry does not exist as a distinct entity in a country’s national accounts leading to difficulties in estimating its role. Besides, the existence of a significant informal sector aggravates the situation. This study used tourism satellite accounts approach to estimate the economic contribution of tourism. Using primary data from various tourism surveys, six core tables of the tourism satellite accounts framework are presented to estimate the direct economic contribution of tourism to Rwanda’s economy in 2014. In this year, a total of 1,219,529 international tourists visited the country while 560,000 residents took part in domestic tourism trips resulting in internal tourism expenditure/consumption amounting to RWF 261.2bn. This generated an estimated RWF 197.5bn as gross value added by the tourism characteristic industries. Direct tourism gross value added was estimated at RWF 120.0bn while direct tourism gross domestic product, a measure of the direct effects of internal tourism consumption on gross domestic product of the economy was computed at RWF 128.3bn (or 2.5% of Rwanda’s gross domestic product) in the year. In addition to the core six tourism satellite accounts tables, the levels of tourism employment (about 89,000 jobs) tourism gross fixed capital formation (slightly over RWF 200bn) and tourism collective consumption (over RWF 7bn) were estimated. Under this study, the international methodological recommendations on tourism satellite accounts were implemented for Rwanda. The contribution of tourism to gross domestic product, employment, investment, and collective consumption was quantified and estimated. Informal sector tourism activities were included in these estimates. Gross fixed capital formation and collective consumption estimates are tentative due to conceptual considerations documented by the methodological framework.

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Asali, Muhammad. "vgets: A command to estimate general-to-specific VARs, Granger causality, steady-state effects, and cumulative impulse–responses." Stata Journal: Promoting communications on statistics and Stata 20, no. 2 (June 2020): 426–34. http://dx.doi.org/10.1177/1536867x20931004.

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Vector autoregression (VAR) estimation is a vital tool in economic studies. VARs, however, can be dimensionally cumbersome and overparameterized. The vgets command allows for a general-to-specific estimation of VARs— overcoming the potential overparameterization—and provides tests for Granger causality, estimates of the long-run effects, and the cumulative impulse–response of each variable in the system; it also offers diagnostics that facilitate a genuinecausality interpretation of the Granger causality tests.

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Royston, Patrick. "Profile Likelihood for Estimation and Confidence Intervals." Stata Journal: Promoting communications on statistics and Stata 7, no. 3 (September 2007): 376–87. http://dx.doi.org/10.1177/1536867x0700700305.

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Normal-based confidence intervals for a parameter of interest are inaccurate when the sampling distribution of the estimate is nonnormal. The technique known as profile likelihood can produce confidence intervals with better coverage. It may be used when the model includes only the variable of interest or several other variables in addition. Profile-likelihood confidence intervals are particularly useful in nonlinear models. The command pllf computes and plots the maximum likelihood estimate and profile likelihood–based confidence interval for one parameter in a wide variety of regression models.

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Guimarães, Paulo. "A Simple Approach to Fit the Beta-binomial Model." Stata Journal: Promoting communications on statistics and Stata 5, no. 3 (September 2005): 385–94. http://dx.doi.org/10.1177/1536867x0500500307.

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In this paper, I show how to estimate the parameters of the beta-binomial distribution and its multivariate generalization, the Dirichlet-multinomial distribution. This approach involves no additional programming, as it relies on an existing Stata command used for overdispersed count panel data. Including covariates to allow for regression models based in these distributions is straightforward.

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Calzolari, Giorgio, Maria Gabriella Campolo, Antonino Di Pino, and Laura Magazzini. "Maximum likelihood estimation of an across-regime correlation parameter." Stata Journal: Promoting communications on statistics and Stata 21, no. 2 (June 2021): 430–61. http://dx.doi.org/10.1177/1536867x211025834.

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In this article, we describe the mlcar command, which implements a maximum likelihood method to simultaneously estimate the regression coefficients of a two-regime endogenous switching model and the coefficient measuring the correlation of outcomes between the two regimes. This coefficient, known as the “across-regime” correlation parameter, is generally unidentified in the traditional estimation procedures.

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Muñoz, Ercio, and Salvatore Morelli. "kmr: A command to correct survey weights for unit nonresponse using groups’ response rates." Stata Journal: Promoting communications on statistics and Stata 21, no. 1 (March 2021): 206–19. http://dx.doi.org/10.1177/1536867x211000025.

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In this article, we describe kmr, a command to estimate a microcompliance function using groups’ nonresponse rates (Korinek, Mistiaen, and Ravallion, 2007, Journal of Econometrics 136: 213–235), which can be used to correct survey weights for unit nonresponse. We illustrate the use of kmr with an empirical example using the current population survey and state-level nonresponse rates.

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Zhou, Hongcheng, Dezhi Xu, and Bin Jiang. "Model Free Command Filtered Backstepping Control for Marine Power Systems." Mathematical Problems in Engineering 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/619430.

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In order to retrain chaotic oscillation of marine power systems which are excited by periodic electromagnetism perturbation, two novel model free command-filtered backstepping control methods are designed in this paper. Firstly, the dynamic model of marine power system based on the two parallel nonlinear models is established. Secondly, extended state observer (ESO) and adaptive neural network observer (NNO) are designed to estimate the velocity signal and the unknown dynamic model. Moreover, the uniform form of ESO and NNO is given. Next, the model free command-filtered backstepping controller is put forward based on the uniform observer form. Finally, the simulation results indicate that the two proposed control algorithms can quickly retrain chaotic oscillation and their effectiveness and potential are amply demonstrated.

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Souza-Rodrigues, Eduardo. "Deforestation in the Amazon: A Unified Framework for Estimation and Policy Analysis." Review of Economic Studies 86, no. 6 (December 6, 2018): 2713–44. http://dx.doi.org/10.1093/restud/rdy070.

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Abstract Deforestation is a matter of pressing global concern, yet surprisingly little is known about the relative efficacy of various policies designed to combat it. This article sets out a framework for measuring the cost effectiveness of alternative policies—both command-and-control and incentive-based—in the Brazilian Amazon. First, I estimate the demand for deforestation on private properties, exploiting regional variation in transportation costs as a means to recover farmers’ responses to permanent policies. Here, rescaling transportation costs using local yields allows me to express changes in farmers’ valuations in dollars per hectare. I then use the estimated demand to infer farmers’ willingness to deforest under different counterfactual policies, such as payments to avoid deforestation and taxes on land use, along with the corresponding potential farmers’ lost surpluses. The results indicate that payment programmes and land use taxes on agricultural land can be highly effective in preserving the rainforest and also be substantially less expensive than command-and-control policies (approximately 8 times less costly). A carbon tax equal to the social cost of carbon could virtually eliminate all agricultural land in the Amazon, given the low agricultural returns there.

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Dihya, Maincer, Mansour Moufid, Boudjedir Chemseddine, and Bounabi Moussaab. "Switched time delay control based on neural network for fault detection and compensation in robot." IAES International Journal of Robotics and Automation (IJRA) 10, no. 2 (June 1, 2021): 91. http://dx.doi.org/10.11591/ijra.v10i2.pp91-103.

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Fault detection in robotic manipulators is necessary for their monitoring and represents an effective support to use them as independent systems. This present study investigates an enhanced method for representation of the faultless system behavior in a robot manipulator based on a multi-layer perceptron (MLP) neural network learning model which produces the same behavior as the real dynamic manipulator. The study was based on generation of residue by contrasting the actual output of the manipulator with those of the neural network; Then, a time delay control (TDC) is applied to compensate the fault, in which a typical sliding mode command is used to delete the time delay estimate produced by the belated signal in order to obtain strong performances. The results of the simulations performed on a model of the SCARA arm manipulator, showed a good trajectory tracking and fast convergence speed in the presence of faults on the sensors. In addition, the command is completely model independent, for both TDC and MLP neural network, which represents a major advantage of the proposed command.

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Zhao, Yujiao, Haisheng Yu, and Shixian Wang. "An Improved Super-Twisting High-Order Sliding Mode Observer for Sensorless Control of Permanent Magnet Synchronous Motor." Energies 14, no. 19 (September 23, 2021): 6047. http://dx.doi.org/10.3390/en14196047.

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This article presents an improved super-twisting high-order sliding mode observer for permanent magnet synchronous motors to achieve high-performance sensorless control. The proposed observer is able to simultaneously estimate rotor position and speed, as well as track parameter disturbances online. Then, according to the back-EMF model, the sensorless observer is further constructed to improve the estimation effect. The estimated rotor position and speed are used to replace the actual values detected by the sensor, and the estimated parameter disturbances are considered as feedback values to compensate the command voltage. In this way, not only is the estimation accuracy improved, but the robustness against uncertainties is also enhanced. Simulation and experimental results show that the proposed observer can effectively track the rotor position and speed and obtain good dynamic and steady-state performance.

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Horio, Ryosuke, Naoki Uchiyama, and Shigenori Sano. "Observer Design for Estimating Support Force Applied by a Human Operator of a Biped Robot." Journal of Advanced Computational Intelligence and Intelligent Informatics 21, no. 4 (July 20, 2017): 744–50. http://dx.doi.org/10.20965/jaciii.2017.p0744.

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The recognition of a robot operator’s intention/command is important in human-robot collaboration systems. This paper presents a novel approach to estimating the human operator’s force applied to a robotic system. In our previous study, we proposed a human-operated biped robot for transporting objects on rough terrain, steps or stairs. In this paper, we consider a new control system for the proposed robot, which enables the estimation of the support force applied by a human operator. The dynamics of the proposed robot are modeled by assuming that a support force applied by an operator is considered as a disturbance to each joint. The observer was designed to estimate the disturbance based on a high-gain observer; it was proven that the observer could estimate the disturbance with sufficient accuracy. Simulation results show that the observer successfully estimated the support force as a disturbance even though the disturbance property was completely unknown. In this study, the proposed biped robot system with the observer was expected to provide support to human operators for the cooperative transportation of objects up the stairs.

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Lian, Cheng Bin, Chen Bai, Zhang Ren, and Xing Yue Shao. "Hypersonic Cruise Vehicle Attitude Control Based on NESO." Applied Mechanics and Materials 427-429 (September 2013): 913–20. http://dx.doi.org/10.4028/www.scientific.net/amm.427-429.913.

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Hypersonic cruise vehicles traverse abroad flight envelope, severe interference and aerodynamic parameters of great uncertainty. Aiming at these problems, the attitude control system is divided into two first-order subsystem based on the backstepping, which improved by introducing the command filter and the error signal correction. simplifies the solution of pseudo control of derivative, and considering the attenuation and noise on the system state. The aerodynamic parameters wide variation range and disturbances were classified into two subsystems uncertainties, and two sets of nonlinear extended state observer (NESO) were used to estimate them. The backstepping controller based on NESO was designed with combined estimated value and backstepping method. Additionally used fuzzy logic to tuning the NESO parameters. Simulation results show that the method can track the control signal accurately, and has good robustness against parameter uncertainty.

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Laks, Jerson, Evandro Silva Freire Coutinho, Washington Junger, Heitor Silveira, Raphael Mouta, Elienai Maria Rubim Baptista, Ana Lucia Barros Contino, et al. "Education does not equally influence all the Mini Mental State Examination subscales and items: inferences from a Brazilian community sample." Revista Brasileira de Psiquiatria 32, no. 3 (June 7, 2010): 223–30. http://dx.doi.org/10.1590/s1516-44462010005000009.

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OBJECTIVE: Mini-Mental State Examination cutoffs have been presented for schooling levels to screen cognitive impairment. However, items may behave differently with regards to education. The objective of this study was to examine the impact of education on MMSE subscales and items. METHOD: Community-dwelling participants aged 65 years or more (n = 990, females = 637, age = 74.1 years, range 65-108) were stratified as illiterate (n = 373), 1-8 (n = 540), 9-12 (n = 63), and more than 12 years of schooling (n = 14) and were screened with MMSE and Pfeffer Functional Activities Questionnaire. To make the Mini-Mental State Examination items comparable, each item was transformed into z scores. Multiple linear regression was used to estimate the effect of schooling on MMSE subs and items controlling for age, sex, and activities of daily life. RESULTS: Temporal and space orientation, attention/calculation, repetition, reading, writing, and drawing scores improved as education increased, but not memory registration, three step command, and naming. Reading and writing displayed the largest coefficients, whereas education exerted no influence on naming and three step command tasks. CONCLUSION: Education does not exert an important effect on naming, three step command, memory registration, and delayed recall. As memory is a key factor for diagnosing dementia, these items could be considered despite education.

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Li, Wenfei, Huiyun Li, Chao Huang, Kun Xu, Tianfu Sun, and Haiping Du. "Observer-Based Coordinated Control for Blended Braking System with Actuator Delay." Actuators 10, no. 8 (August 11, 2021): 193. http://dx.doi.org/10.3390/act10080193.

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The coordinated control of a blended braking system is always a difficult task. In particular, blended braking control becomes more challenging when the braking actuator has an input time-delay and some states of the braking system cannot be measured. In order to improve the tracking performance, a coordinated control system was designed based on the input time-delay and state observation for a blended braking system comprising a motor braking system and friction braking system. The coordinated control consists of three parts: Sliding mode control, a multi-input single-output observer, and time-delay estimation-based Smith Predictor control. The sliding mode control is used to calculate the total command braking torque according to the desired braking performance and vehicle states. The multi-input single-output observer is used to simultaneously estimate the input time-delay and output braking torque of the friction braking system. With time-delay estimation-based Smith Predictor control, the friction braking system is able to effectively track the command braking torque of the friction braking system. The tracking of command braking torque is realized through the coordinated control of the motor braking system and friction braking system. In order to validate the effectiveness of the proposed approach, numerical simulations on a quarter-vehicle braking model were performed.

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Dippel, Christian, Andreas Ferrara, and Stephan Heblich. "Causal mediation analysis in instrumental-variables regressions." Stata Journal: Promoting communications on statistics and Stata 20, no. 3 (September 2020): 613–26. http://dx.doi.org/10.1177/1536867x20953572.

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In this article, we describe the use of ivmediate, a new command to estimate causal mediation effects in instrumental-variables settings using the framework developed by Dippel et al. (2020, unpublished manuscript). ivmediate allows estimation of a treatment effect and the share of this effect that can be attributed to a mediator variable. While both treatment and mediator can be potentially endogenous, a single instrument suffices to identify both the causal treatment and the mediation effects.

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Schunck, Reinhard, and Francisco Perales. "Within- and Between-cluster Effects in Generalized Linear Mixed Models: A Discussion of Approaches and the Xthybrid command." Stata Journal: Promoting communications on statistics and Stata 17, no. 1 (March 2017): 89–115. http://dx.doi.org/10.1177/1536867x1701700106.

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One typically analyzes clustered data using random- or fixed-effects models. Fixed-effects models allow consistent estimation of the effects of level-one variables, even if there is unobserved heterogeneity at level two. However, these models cannot estimate the effects of level-two variables. Hybrid and correlated random-effects models are flexible modeling specifications that separate within-and between-cluster effects and allow for both consistent estimation of level-one effects and inclusion of level-two variables. In this article, we elaborate on the separation of within- and between-cluster effects in generalized linear mixed models. These models present a unifying framework for an entire class of models whose response variables follow a distribution from the exponential family (for example, linear, logit, probit, ordered probit and logit, Poisson, and negative binomial models). We introduce the user-written command xthybrid, a shell for the meglm command. xthybrid can fit a variety of hybrid and correlated random-effects models.

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Journal articles on the topic 'Command Estimate'

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