a. What are differences between the single-factor research design and factorial research designs?
 b. What does it mean for there to be (or not be) an interaction effect between independent variables?
 c. Looking at a figure of cell means, what would indicate an interaction effect is present?
d. What is the difference between cell means and marginal means? What is represented by each of these two types of means?
e. What is the relationship between the presence or absence of main effects and the presence or absence of interaction effects?
f. Why does a determination of an interaction effect precede an examination of main effects?
 g. Compared with the single-factor research design, what are the advantages and disadvantages of factorial research designs?
