Controls are needed in a case‐control study because:
A)They may be followed to determine if they have the disease in question
B)They increase the sample size so that statistical significance can be achieved
C)They provide a comparable estimate of the frequency of exposure in the absence of disease
D)They are matched to cases on suspected risk factors

Question

Quizplus · Accepted Answer

They provide an estimate of the frequency of exposure in the absence of
disease which can then be compared to the frequency of the same exposure in cases.
Without controls we would not know if an exposure was associated with the disease.

Controls Are Needed in a Case‐control Study Because