DrNan Is Studying the Effects of Ginseng on Recall

Multiple Choice

Dr.Nan is studying the effects of Ginseng on recall.He has 2 groups of subjects, (20 subjects in each group) .Subjects are given Ginseng or Placebo and then asked to recall a list of words they previously studied.However,to avoid confounds what should Dr.Nan do?

A) Counterbalance placebo & Ginseng
B) Match groups on an IQ test and assign to groups
C) Randomly assign subjects to groups
D) All of these
E) None of these