Cohort, case-control and cross-sectional sampling methods MCQs With Answer

Cohort, case-control and cross-sectional sampling methods MCQs With Answer

Introduction: This quiz collection is designed for M.Pharm students preparing for Clinical Research (MPP 104T). It focuses on sampling methods and study designs—cohort, case-control and cross-sectional—emphasizing their sampling strategies, measures of association, strengths, limitations and common biases. Questions probe both conceptual understanding (temporality, incidence vs prevalence, matching, nested designs) and practical aspects (person-time, attributable risk, sampling choices for prevalence surveys). Each question includes four options and the correct answer to help you evaluate readiness for exams and real-world study planning. Use these targeted MCQs to sharpen critical thinking about design selection, bias control and interpretation of effect measures.

Q1. Which study design is most appropriate to examine the effect of a rare exposure on subsequent development of disease?

• Cohort study
• Case-control study
• Cross-sectional study
• Randomized controlled trial

Correct Answer: Cohort study

Q2. Which design is most efficient for studying a rare disease?

• Cohort study
• Case-control study
• Cross-sectional study
• Ecological study

Correct Answer: Case-control study

Q3. Which measure of effect is directly obtained from a cohort study comparing cumulative incidence in exposed and unexposed groups?

• Odds ratio
• Relative risk (risk ratio)
• Prevalence ratio
• Attributable fraction in the population

Correct Answer: Relative risk (risk ratio)

Q4. Which measure is the primary effect estimate in a conventional case-control study?

• Risk difference
• Relative risk
• Odds ratio
• Incidence rate

Correct Answer: Odds ratio

Q5. A cross-sectional study primarily measures which epidemiologic parameter?

• Incidence
• Person-time rate
• Prevalence
• Hazard rate

Correct Answer: Prevalence

Q6. Which study design best establishes temporality between exposure and outcome?

• Prospective cohort study
• Case-control study
• Cross-sectional study
• Ecologic study

Correct Answer: Prospective cohort study

Q7. When calculating incidence rates using person-time, which study design is most suitable?

• Cross-sectional study
• Case-control study
• Cohort study
• Case series

Correct Answer: Cohort study

Q8. Which statement correctly describes a nested case-control study?

• Cases and controls are selected from different populations to increase variability
• Cases and controls are randomly selected from the general population without cohort context
• Cases and controls are drawn from a well-defined cohort, with controls selected from risk sets
• Controls are selected after outcome occurs using convenience sampling

Correct Answer: Cases and controls are drawn from a well-defined cohort, with controls selected from risk sets

Q9. What is the primary purpose of matching in a case-control study?

• To increase case recruitment rate
• To control confounding by the matched factors
• To blind investigators to exposure status
• To measure incidence directly

Correct Answer: To control confounding by the matched factors

Q10. Which type of bias is particularly problematic in case-control studies when exposure information is collected by participant recall?

• Selection bias due to loss to follow-up
• Recall bias
• Observer bias in outcome assessment
• Surveillance bias

Correct Answer: Recall bias

Q11. For a nationwide prevalence survey where logistical costs and travel are limiting, which sampling strategy is most practical?

• Simple random sampling of individuals nationwide
• Stratified sampling with proportional allocation
• Cluster sampling (multistage)
• Systematic sampling from a single registry

Correct Answer: Cluster sampling (multistage)

Q12. Which sampling method ensures representation of important subgroups and can reduce sampling variability for prevalence estimates?

• Simple random sampling
• Stratified sampling
• Convenience sampling
• Snowball sampling

Correct Answer: Stratified sampling

Q13. In case-control studies, increasing the number of controls per case generally increases power up to a practical limit. Which control-to-case ratio yields substantial extra power without excessive cost?

• 1:1
• 2:1
• 4:1
• 10:1

Correct Answer: 4:1

Q14. Which statement best characterizes a retrospective cohort study?

• Exposure and outcome are assessed prospectively from the point of enrollment
• Participants are randomized to exposure groups
• Both exposure and outcome have already occurred; historical records are used
• Only prevalent cases are assessed at a single time point

Correct Answer: Both exposure and outcome have already occurred; historical records are used

Q15. What is the formula for attributable risk percent among the exposed (AR% among exposed) when relative risk (RR) is known?

• (RR) × 100
• (RR − 1) × 100
• ((RR − 1) / RR) × 100
• ((1 − RR) / RR) × 100

Correct Answer: ((RR − 1) / RR) × 100

Q16. Which study design is most efficient for assessing multiple outcomes that may arise from a single exposure?

• Case-control study
• Cross-sectional study
• Cohort study
• Ecologic study

Correct Answer: Cohort study

Q17. What is the major limitation of cross-sectional studies when interpreting causal relationships?

• High cost compared with cohort studies
• Inability to establish temporality between exposure and outcome
• Requirement for long follow-up
• They always require matching of cases and controls

Correct Answer: Inability to establish temporality between exposure and outcome

Q18. In cohort studies, which issue most commonly leads to selection bias affecting effect estimates?

• Differential misclassification of exposure at baseline
• Loss to follow-up that differs by exposure and outcome risk
• Recall bias due to retrospective interviews
• Confounding by indication only

Correct Answer: Loss to follow-up that differs by exposure and outcome risk

Q19. Under what condition does the odds ratio from a case-control study approximate the relative risk?

• When the exposure is very common
• When the outcome is rare (rare disease assumption)
• When matching is used for all confounders
• When the study is cross-sectional

Correct Answer: When the outcome is rare (rare disease assumption)

Q20. To estimate the current prevalence of hypertension in a city with age-related variation, which approach is most appropriate?

• Prospective cohort study enrolling normotensive persons
• Case-control study selecting hypertensive cases and normotensive controls
• Cross-sectional survey using stratified random sampling by age groups
• Randomized controlled trial of antihypertensive drugs

Correct Answer: Cross-sectional survey using stratified random sampling by age groups

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