Cross-sectional study design and interpretation MCQs With Answer

Introduction: Cross-sectional study design and interpretation MCQs With Answer is a focused question bank tailored for M.Pharm students studying pharmacoepidemiology and pharmacoeconomics. This set explores methodological principles, sampling strategies, measures of frequency and association, bias sources, analytical choices and interpretation challenges specific to cross-sectional studies. Each MCQ emphasizes practical decision-making — choosing appropriate measures (prevalence, prevalence ratio, odds), addressing confounding, handling sampling and weighting, and understanding limitations for causal inference. Questions progress from foundational concepts to applied scenarios that mimic real research and surveillance problems, helping students consolidate knowledge needed for exam success and research design in pharmaceutical epidemiology.

Q1. Which measure is the primary outcome estimated directly from a single cross-sectional survey?

• Incidence rate
• Period prevalence
• Point prevalence
• Risk difference

Correct Answer: Point prevalence

Q2. Which statement best distinguishes a cross-sectional study from a cohort study?

• Cross-sectional studies follow individuals over time to measure new events
• Cohort studies measure exposure and outcome at the same single time-point
• Cross-sectional studies assess exposure and outcome simultaneously at one time-point
• Cohort studies always use random sampling from a population

Correct Answer: Cross-sectional studies assess exposure and outcome simultaneously at one time-point

Q3. What is the main reason cross-sectional studies are limited for establishing causality?

• They always use small sample sizes
• They cannot determine temporality between exposure and outcome
• They are unable to measure prevalence
• They are more expensive than randomized trials

Correct Answer: They cannot determine temporality between exposure and outcome

Q4. For estimating population prevalence with reduced sampling error across age groups, which sampling strategy is most appropriate in a cross-sectional survey?

• Purposive sampling
• Simple random sampling without stratification
• Stratified random sampling
• Convenience sampling at clinics

Correct Answer: Stratified random sampling

Q5. In a cross-sectional study assessing association between smoking and chronic cough, which measure is most directly interpretable as relative prevalence?

• Prevalence ratio
• Incidence rate ratio
• Hazard ratio
• Attributable risk percent

Correct Answer: Prevalence ratio

Q6. When outcome prevalence is common (>10%), which measure derived from logistic regression can substantially overestimate the association compared with the prevalence ratio?

• Adjusted prevalence ratio from Poisson regression
• Adjusted odds ratio from logistic regression
• Risk difference from linear regression
• Incidence rate ratio from Cox regression

Correct Answer: Adjusted odds ratio from logistic regression

Q7. Which factor is NOT directly used to calculate sample size for estimating a prevalence with a desired precision in a cross-sectional study?

• Expected prevalence
• Desired confidence level (e.g., 95%)
• Acceptable margin of error
• Number of study sites

Correct Answer: Number of study sites

Q8. If non-responders differ systematically from responders with respect to both exposure and outcome, what bias is most likely introduced?

• Selection bias (non-response bias)
• Information bias due to misclassification
• Confounding by indication
• Performance bias

Correct Answer: Selection bias (non-response bias)

Q9. Weighting survey data in complex cross-sectional designs is primarily used to:

• Increase response rates during data collection
• Account for unequal probabilities of selection and improve representativeness
• Eliminate measurement error in exposure assessment
• Convert prevalence into incidence

Correct Answer: Account for unequal probabilities of selection and improve representativeness

Q10. Which of the following is a major strength of cross-sectional studies in pharmacoepidemiology?

• They are ideal for establishing cause-and-effect relationships
• They efficiently estimate the burden (prevalence) of medication use and adverse events
• They directly measure incidence of rare adverse events over time
• They always require prospective follow-up

Correct Answer: They efficiently estimate the burden (prevalence) of medication use and adverse events

Q11. A cross-sectional study shows an association between high salt intake and current hypertension. Which explanation must be considered before inferring causality?

• Reverse causation (hypertensive patients reducing salt)
• Temporal precedence is clearly established
• Incidence of hypertension was measured
• Loss to follow-up biased the result

Correct Answer: Reverse causation (hypertensive patients reducing salt)

Q12. An observed prevalence ratio of 2.5 for exposure and disease means:

• The exposure causes disease in 2.5% of those exposed
• The prevalence of disease among exposed is 2.5 times the prevalence among unexposed
• The incidence among exposed is 2.5 times higher
• The attributable risk in the population is 2.5

Correct Answer: The prevalence of disease among exposed is 2.5 times the prevalence among unexposed

Q13. Non-differential misclassification of a binary exposure in a cross-sectional study typically biases the measure of association towards:

• The null (no association)
• An extreme value away from the null
• Increased precision of the estimate
• Selection of a more representative sample

Correct Answer: The null (no association)

Q14. Which design is most appropriate to examine secular trends in prevalence of drug use over a decade?

• Single cross-sectional survey at baseline only
• Repeated cross-sectional surveys at multiple time points
• Retrospective case-control study
• Randomized controlled trial

Correct Answer: Repeated cross-sectional surveys at multiple time points

Q15. How should investigators handle seasonal variation when planning a cross-sectional survey of respiratory symptom prevalence?

• Conduct the survey only in the peak season to maximize cases
• Ignore seasonality because prevalence is stable
• Sample across seasons or adjust analyses for season of measurement
• Use incidence measures instead of prevalence

Correct Answer: Sample across seasons or adjust analyses for season of measurement

Q16. In cluster sampling for community cross-sectional surveys, the intra-cluster correlation coefficient (ICC) primarily affects:

• The validity of exposure measurement instruments
• The required sample size (design effect) and variance estimates
• The direction of association between exposure and outcome
• The ability to compute point prevalence only

Correct Answer: The required sample size (design effect) and variance estimates

Q17. A 95% confidence interval for a prevalence estimate that does not include 0 indicates:

• The sample is biased
• Statistical significance is irrelevant for prevalence
• The estimated prevalence is unlikely to be zero in the population
• The prevalence must be greater than 50%

Correct Answer: The estimated prevalence is unlikely to be zero in the population

Q18. To control for confounding when estimating adjusted prevalence ratios in cross-sectional data, which analytical method is often recommended?

• Standard logistic regression reporting odds ratios without modification
• Poisson regression with robust standard errors or log-binomial regression
• Simple stratification only without regression
• Kaplan-Meier survival analysis

Correct Answer: Poisson regression with robust standard errors or log-binomial regression

Q19. Which sampling frame problem can lead to systematic underestimation of medication non-adherence in a population survey?

• Including too many rural households
• Using outdated phone lists that omit younger, mobile populations
• Oversampling minorities intentionally
• Weighting responses to match population demographics

Correct Answer: Using outdated phone lists that omit younger, mobile populations

Q20. Which statement about cross-sectional studies and incidence is correct?

• Cross-sectional studies directly measure incidence of new cases
• Incidence can only be estimated from cross-sectional data if recall of onset period is accurate and appropriate methods are applied
• Cross-sectional designs always provide reliable incidence rates for chronic diseases
• Incidence is irrelevant to pharmacoepidemiology

Correct Answer: Incidence can only be estimated from cross-sectional data if recall of onset period is accurate and appropriate methods are applied

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