Detecting Changes of Level and Slope in Repeated-Measures Data

Abstract

This article examines the following situation: A variable is measured for a sample of subjects on several occasions before and after an experimental intervention thought to affect the variable. This situation had broad application in the social sciences and elsewhere. The article introduces MANOVA tests for changes in level and slope that arise as a consequence of the intervention. These methods are illustrated using data from a social-psychological study. The approach may be extended to studies in which there are several groups of subjects.