1. Using the factorial design allows one to overcome the following limitations of the simple experiment:
a. Only studying one variable at a time;
b. Only studying situational variables (but emphasize that if they use a personality factor as their second variable in a factorial study, they can't make causal inferences about this variable [see Table 12.12]);
c. Not knowing whether a main effect would generalize to different situations, persons, places, or conditions (a significant interaction involving situations, subject type or location indicates that the effect would not generalize);
d. Lack of power due to not controlling or accounting for effects of other variables.
2. Factorial designs allow students to build on existing studies and test several hypotheses in a single study.