What Effect Do Within-Subjects Designs Have on the Number of Research

Multiple Choice

What effect do within-subjects designs have on the number of research participants?

A) It increases the number needed since the error variance increases.
B) It increases the number needed because the F ratio tends to be larger.
C) It reduces the number needed since each participant serves as her own control.
D) It reduces the number needed since most studies of this type are concerned with populations that are small.