In a study designed to examine the effects of caffeine on reaction time, four caffeine conditions 100, 200, 300, and 400 mg of caffeine) are used. If the experimenter decides to use complete counterbalancing and assuming that one subject will be tested in each of the sequences used, how many people will be needed to complete the study?
A) 24
B) 48
C) 12
D) 4

Question

Quizplus · Accepted Answer

Complete counterbalancing requires testing all possible sequences of conditions. With four conditions, there are 4! (4 factorial) sequences, which equals 4 x 3 x 2 x 1 = 24. Therefore, 24 people are needed to test each sequence once.

In a Study Designed to Examine the Effects of Caffeine