Diagnostic and Treatment for Linear Mixed Models

Júlio M. Singer
Departamento de Estatística - IME
Universidade de São Paulo - Brasil

We review some results on the analysis of longitudinal data or, more generally, of repeated measures via linear mixed models starting with some exploratory statistical tools that may be employed to specify a tentative model. We follow with a summary of inferential procedures under a Gaussian set-up and then discuss different diagnostic methods focusing on residual analysis but also addressing global and local influence. Based on the interpretation of diagnostic plots related to three types of residuals (marginal, conditional and predicted random effects) as well as on other tools, we proceed to identify remedial measures for possible violations of the proposed model assumptions, ranging from fine-tuning of the model to the use of elliptically-symmetric or skew-elliptical linear mixed models as well as of robust estimation methods. We specify many results available in the literature in a unified notation and highlight those with greater practical appeal. In each case we discuss the availability of model diagnostics as well as of software and  give general guidelines for model selection. We conclude with analyses of three practical examples and suggest further directions for research.

Uma Introdução à Teoria de Resposta ao Item (TRI)

Dalton Andrade
Departamento de Informática e Estatística
Universidade Federal Santa Catarina - Brasil

Neste seminário iremos apresentar e discutir as principais ideias, conceitos e aplicações da TRI. Na primeira parte, vamos focar nos conceitos da TRI, nos seus modelos unidimensionais para itens dicotômicos e politômicos, nos métodos de estimação e equalização e na construção de escala. Na segunda parte, vamos focar em várias aplicações de TRI em diversas áreas, tais como Avaliação Educacional, Meio Ambiente, Enfermagem e Administração.