Describe an IV × PV factorial design.

Why would a researcher have more than two levels of the independent variable in an experiment?
What is a factorial design? Why would a researcher use a factorial design?
What are main effects in a factorial design? What is an interaction?
Describe an IV × PV factorial design.
Identify the number of conditions in a factorial design on the basis of knowing the number of independent variables and the number of levels of each independent variable.
Describe 2 × 2 factorial designs in which (a) both independent variables are independent groups (between-subjects), (b) both independent variables are repeated measures (within-subjects), and (c) the design is mixed, so that one independent variable is independent groups and the other is repeated measures.