Fixed Effects Regression Methods for Longitudinal Data Using SAS

3.1. Introduction

In this chapter we consider fixed effects regression models for response variables that are categorical: dichotomous, unordered polytomous, and ordered polytomous. In chapter 2 we saw that linear fixed effects models for quantitative response variables could be estimated in several different ways, all producing the same results. Analogous methods are also available for categorical response variables, but these methods typically do not produce exactly the same results. So an important task of this chapter is to clarify the differences among the different methods and to develop appropriate interpretations of their coefficients.

In chapter 1 we saw that the paired-comparisons t-test could be interpreted as a fixed effects method. ...