In a Study That Seeks to Evaluate the Effect Caffeine

Multiple Choice

In a study that seeks to evaluate the effect caffeine has on narcoleptics,40 narcoleptic patients 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 in this study is the:

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