How many participants would be needed for a within-subjects experiment comparing four different treatment conditions with a total of 20 scores in each treatment?
A) 20
B) 40
C) 80
D) Anywhere from 20 to 80

Question

Quizplus · Accepted Answer

In a within-subjects design, each participant experiences all treatment conditions. Therefore, if there are 20 scores needed for each of the four conditions, only 20 participants are needed, as each participant provides one score per condition.

How Many Participants Would Be Needed for a Within-Subjects Experiment