MCCQE Population Health and Epidemiology 3 — Questions and Answers
Question 1: A researcher finds an odds ratio of 2.5 (95% CI: 0.9–6.8) for the association between a dietary factor and colon cancer. What is the correct interpretation?
- There is a statistically significant association
- The result is not statistically significant at the 0.05 level (Correct answer)
- The dietary factor is definitively protective
- The study has insufficient external validity
Correct answer: The result is not statistically significant at the 0.05 level
Because the 95% CI crosses 1.0, the result is not statistically significant at α = 0.05.
Question 2: Which epidemiological study design provides the strongest evidence for causality?
- Case series
- Ecological study
- Randomized controlled trial (Correct answer)
- Case-control study
Correct answer: Randomized controlled trial
Randomized controlled trials minimize confounding through randomization, providing the strongest causal evidence.
Question 3: In Bradford Hill's criteria, which criterion addresses the plausibility of the cause-effect relationship based on current biological knowledge?
- Temporality
- Coherence
- Biological plausibility (Correct answer)
- Specificity
Correct answer: Biological plausibility
Biological plausibility requires that the association makes sense given existing biological and medical knowledge.
Question 4: A screening test for colorectal cancer is applied to 10,000 people; 200 test positive, 50 have true disease (all test positive), and 150 are false positives. What is the specificity?
- 75%
- 98.4% (Correct answer)
- 25%
- 100%
Correct answer: 98.4%
Specificity = TN / (TN + FP) = 9,800 / (9,800 + 150) = 9,800/9,950 ≈ 98.5%.
Question 5: Which of the following best describes a systematic review?
- A single large observational study
- A comprehensive synthesis of all relevant studies on a topic using explicit methods (Correct answer)
- An expert opinion on a clinical question
- A narrative literature review without defined search criteria
Correct answer: A comprehensive synthesis of all relevant studies on a topic using explicit methods
Systematic reviews use pre-specified, reproducible search and selection criteria to synthesize evidence from multiple studies.
Question 6: What does the number needed to harm (NNH) represent?
- The probability that a given patient will experience harm
- The number of patients who must be treated for one additional patient to experience harm (Correct answer)
- The relative risk increase due to an intervention
- The absolute risk difference between two groups
Correct answer: The number of patients who must be treated for one additional patient to experience harm
NNH = 1 / absolute risk increase; it quantifies how many patients need treatment before one additional harmful event occurs.
Question 7: Which of the following is the primary goal of primary prevention?
- Early detection of disease before symptoms appear
- Reducing the prevalence of an established disease
- Preventing the occurrence of disease in healthy individuals (Correct answer)
- Minimizing disability after disease onset
Correct answer: Preventing the occurrence of disease in healthy individuals
Primary prevention targets risk factor reduction to prevent disease from ever occurring in at-risk populations.
MCCQE Population Health and Epidemiology 3
A researcher finds an odds ratio of 2.5 (95% CI: 0.9–6.8) for the association between a dietary factor and colon cancer.
What is the correct interpretation?