In a Study That Seeks to Evaluate the Effect That

Multiple Choice

In a study that seeks to evaluate the effect that caffeine has on individuals with narcolepsy, 40 patients with this condition are randomly selected to participate in the study.Fifteen of the patients are given high doses of caffeine, 15 are given moderate doses, and 10 are given low doses over a period of 30 days.The variable of interest in this study is:

A) the 40 narcoleptic patients.
B) the period of 30 days.
C) the dosage of caffeine administered.
D) the sample size used.