Question

What is NOT true about a case control study?

• A. It gives attributable risk
• B. It is less expensive
• C. It involves fewer subjects
• D. It provides quick results

Hint:

Case control studies work backward from disease to exposure and give an odds ratio, not incidence based measures like attributable risk.

Answer 1

The Correct Option is A

This question checks the basic features of a case control study, one of the two major observational designs used in epidemiology along with the cohort study.

1. It gives attributable risk: A case control study samples people by disease status, not by exposure status, so the true incidence of disease among exposed and unexposed people stays unknown. Attributable risk needs that incidence data, so a case control study cannot give it directly. This is the false statement.
2. It is less expensive: True. There is no long follow up period, and the sample size stays small, so the running cost stays low.
3. It involves fewer subjects: True. Cases of even a rare disease can be pulled from hospital records, and each case needs only one or a few matched controls, so the total subject count stays small.
4. It provides quick results: True. Since the disease outcome has already happened by the time the study starts, there is no need to wait years for it to occur, so results are ready sooner than in a cohort study.

The correct answer is that a case control study gives attributable risk, since this is the one claim that does not hold up. A case control study can only estimate relative risk through the odds ratio, never attributable risk.

Let's summarize:

• Case control studies work backward from disease to exposure and rely on an odds ratio, not incidence.
• They are cheap, quick, and need fewer subjects compared with a cohort study.

So the statement that does not hold true for a case control study is that it gives attributable risk.