Web-based Supplementary Materials for “Bayesian Semiparametric Nonlin- ear Mixed-Effects Joint Models for Data with Skewness, Missing Responses and Measurement Errors in Covariates” by Y. Huang and G. Dagne Web Appendix A. Multivariate Skew Distributions
ثبت نشده
چکیده
Web Appendix A. Multivariate Skew Distributions Different versions of the multivariate skew–normal(SN) and skew-t (ST) distributions have been considered and used in the literature (Arellano-Valle and Genton, 2005; Arellano-Valle et al, 2007; Azzalini and Capitanio, 2003; Sahu et al, 2003 and among others). A new class of distributions by introducing skewness in multivariate elliptically distributions were developed in publication (Sahu et al, 2003). The class, which is obtained by using transformation and conditioning, contains many standard families including the multivariate SN and ST distributions. For completeness, this appendix briefly summarizes the multivariate SN and ST distributions that will be used in defining the skew BNLME joint models considered in this paper. Assume an m-dimensional random vector Y follows an m variate SN or ST distribution with location vector μ, m ×m positive (diagonal) dispersion matrix Σ and m ×m skewness matrix ∆(δ) = diag(δ1, δ2, . . . , δm) or the degrees of freedom ν, where δ = (δ1, . . . , δm) T . In what follows, we briefly discuss multivariate SN and ST distributions introduced by Sahu et al(2003) which are suitable for a Bayesian inference since they is built using conditional method. For detailed discussions on properties of SN and ST distributions, see Reference (Sahu et al, 2003).
منابع مشابه
Mixed-effects joint models with skew-normal distribution for HIV dynamic response with missing and mismeasured time-varying covariate.
Longitudinal data arise frequently in medical studies and it is a common practice to analyze such complex data with nonlinear mixed-effects (NLME) models, which enable us to account for between-subject and within-subject variations. To partially explain the variations, time-dependent covariates are usually introduced to these models. Some covariates, however, may be often measured with substant...
متن کاملMixed-Effects Tobit Joint Models for Longitudinal Data with Skewness, Detection Limits, and Measurement Errors
Complex longitudinal data are commonly analyzed using nonlinearmixed-effects NLME models with a normal distribution. However, a departure fromnormalitymay lead to invalid inference and unreasonable parameter estimates. Some covariates may be measured with substantial errors, and the response observations may also be subjected to left-censoring due to a detection limit. Inferential procedures ca...
متن کاملBayesian inference for a nonlinear mixed-effects Tobit model with multivariate skew-t distributions: application to AIDS studies.
Censored data are characteristics of many bioassays in HIV/AIDS studies where assays may not be sensitive enough to determine gradations in viral load determination among those below a detectable threshold. Not accounting for such left-censoring appropriately can lead to biased parameter estimates in most data analysis. To properly adjust for left-censoring, this paper presents an extension of ...
متن کاملA Bayesian Approach for Joint Modeling of Skew-normal Longitudinal Measure- Ments and Time to Event Data
• Joint modeling of longitudinal measurements and survival time has an important role in analyzing medical data sets. For example, in HIV data sets, a biological marker such as CD4 count measurements is considered as a predictor of survival. Usually, longitudinal responses of these studies are severely skew. An ordinary method for reducing the skewness is the use of square root or logarithm tra...
متن کاملA Bayesian Semiparametric Model for Case - ControlStudies with Errors
We develop a model and a numerical estimation scheme for a Bayesian approach to inference in case-control studies with errors in covariables. The model proposed in this paper is based on a nonparametric model for the unknown joint distribution for the missing data, the observed covariates and the proxy. This nonparametric distribution deenes the measurement error component of the model which re...
متن کامل