ABSTRACT
In this chapter you will:
Learn how to analyze data from a two-factor study when factors are mixed, one between subjects and one within subjects.
Learn how to analyze data from a two-factor study when both factors are within subjects.
Learn how to compute the degrees of freedom associated with the main effects and interactions for these two kinds of repeated-measures studies.
Learn how to perform post hoc tests for analyses involving repeated measures.
The two studies presented in the last chapter included a single repeated measure or within-subjects factor. Subjects were assessed more than once and the levels of the within-subjects factor formed the repeated assessments or groups for analysis. Thus for the last example, subjects were presented with videotapes of four infants, each with a different diagnosis. The purpose of the analysis was to determine whether the mean number of times subjects pushed the button was significantly different for infants with different diagnoses. Each subject saw videotapes representing all four diagnostic groups, so our only concern was with variability within subjects. Variability between subjects was irrelevant to the question at hand, which involved within-subject effects, and for that reason it was removed from consideration, or statistically controlled, at the outset.