Effect Sizes for Factorial Designs

In this chapter we discuss a variety of estimators of standardized-difference and strength-of-association effect sizes for factorial designs with fixed-effects factors. Prior to the section on within-groups designs the discussion and examples involve only between-groups factors. The discussions of estimators of standardized differences are much influenced by the seminal work of Cortina and Nouri (2000) and Olejnik and Algina (2000). We add some alternative approaches and some of our own perspectives, focusing on assumptions, the nature of the populations to which results are to be generalized, and pairwise comparisons.