Which would be the best method to increase the positive predictive value of a screening test?

Correct Answer: B

Rationale: The positive predictive value is affected by what proportion of the tested population has the problem. To increase the positive predictive value, screen populations most at risk for the problem. Testing a large population at once, using a very sensitive or very specific screening test would not increase the positive predictive value of a screening test.

Correct Answer: B

Rationale: Incidence (B) measures new cases over a period, reflecting disease onset. Prevalence (A) is total cases, morbidity (C) is disease burden broadly, and mortality (D) is deaths, not new cases.

Correct Answer: C

Rationale: Case-control studies (C) compare diseased (cases) and non-diseased (controls) to assess past exposures. A measures prevalence, B follows exposure, D tests interventions.

Correct Answer: C

Rationale: Primary prevention (C) prevents disease onset via education/promotion (e.g., vaccination). A is secondary, B is tertiary, D is monitoring.

Correct Answer: D

Rationale: Attrition bias (D) arises from differential loss to follow-up affecting results (e.g., in cohorts). A is selection, B is data error, C is recall.