A researcher attempts to study the effects of alcohol on task performance. One factor is alcohol-alcohol treatment versus placebo control-and the other factor is task difficulty-easy versus difficult. If the researcher uses a completely repeated measures design with 15 participants per condition, how many participants will he need for the study?
A)15
B)30
C)45
D)60

Question

Quizplus · Accepted Answer

In a completely repeated measures design, each participant is exposed to all levels of each independent variable. Since there are two factors (alcohol treatment vs. placebo and task difficulty easy vs. difficult), each participant will go through all combinations of these factors. Therefore, the researcher only needs 15 participants in total, as each of the 15 will be used in each condition.

A Researcher Attempts to Study the Effects of Alcohol on Task