APPROXIMATE DEGREES OF FREEDOM TESTS - A UNIFIED PERSPECTIVE ON TESTING FOR MEAN EQUALITY

This article presents a statistic for tests of mean equality in between-subjects and within-subjects designs when variances are heterogeneous. The approximate degrees of freedom statistic of S. Johansen (1980) can be used to test main and interaction effects, as well as multiple comparison hypotheses related to these effects. Thus, researchers need only be familiar with a single statistic, rather than the many statistics that have been defined in the literature, to perform these tests of significance. Also included is a computer program to obtain a numerical solution.