Analyzing change in categorical variables by generalized log-linear models

This article discusses how several hypotheses about change in discrete vari ables can be rested on data obtained in a longitudinal study. A first class of hypotheses pertain to the invariance of certain characteristics of marg inal distributions. A second class of hypotheses derive from assumptions ab out the causal relations between the variables. In this article, the author s show how all these hypotheses can be tested by means of a generalization of log-linear modeling developed by Lang and Agresti. By means of the same approach, it is also possible to test conjunctions of several hypotheses fr om both classes.