ABSTRACT
In this chapter you will:
Learn what between-subjects factorial studies are and what advantages they offer.
Learn how to construct predictor variables for analyzing data from between-subjects factorial studies.
Learn how to compute the degrees of freedom associated with the main effects and interactions of these studies.
Learn how to determine whether the main effects and interactions (i.e., conditional relationships) of these studies are statistically significant and how to characterize the magnitude of such effects.
Learn how to interpret any statistically significant main effects and interactions.
In chapter 10 you learned how to decide if two groups differ significantly and in chapter 12 you learned how to perform an analysis of variance with more than two groups. As you now know, no matter the number of groups, you need only determine whether a single between-subjects factor significantly increases predictability. The single factor in such studies indicates group membership—for example, whether subjects were assigned to an experimental or a control group, or to which of four different want/have children status groups subjects belonged. Subjects in these studies are assigned or belong to one, and only one, of the groups; that is, the groups in the studies are formed independently. Such studies can be visualized as a single row of cells, with each cell representing a group and containing the subjects belonging to that group (see Fig. 14.1).