Which statement correctly describes a factorial design?

• A. A simple two-group design tests one independent variable with two levels.
• B. A factorial design cannot test interactions.
• C. A factorial design uses repeated measures for all participants.
• D. A factorial design tests more than one independent variable and their interactions.

Answer: (D)

Factorial designs explore how two or more independent variables influence a dependent variable, and they reveal how those variables work together through interactions. By crossing factors and examining all combinations, you can see not only the separate effects of each variable (main effects) but also whether the effect of one variable depends on the level of another. For example, you might vary drug dose and therapy type, each with multiple levels, and look at how outcomes change across all combinations. This design is flexible: you can use between-subjects, within-subjects, or mixed arrangements, so it’s not about everyone experiencing every condition. That’s why the statement that best describes a factorial design is that it tests more than one independent variable and their interactions.