Dr. James wants to perform a within-subjects experiment that involves four levels of an independent variable. He wants to control for order and sequence effects using complete counterbalancing within a group of subjects. What is the minimum number of subjects that he will need?
A) 2
B) 4
C) 24
D) 120

Question

Quizplus · Accepted Answer

In complete counterbalancing within a group of subjects, the number of possible orders of presentation of the levels is equal to the factorial of the number of levels. So for four levels there are 4! = 24 possible orders. To control for order and sequence effects, each subject needs to participate in all 24 possible orders. Therefore, the minimum number of subjects required is 24, because each subject can be used to represent one order in the counterbalancing design.

Dr James Wants to Perform a Within-Subjects Experiment That Involves