Experimental, quasi-experimental and observational designs MCQs With Answer

Introduction: This set of multiple-choice questions focuses on experimental, quasi-experimental, and observational study designs relevant to Clinical Research (MPP 104T) for M.Pharm students. The questions cover core concepts such as randomization, control groups, blinding, internal and external validity, cohort and case-control methodologies, crossover and cluster trials, interrupted time-series, regression discontinuity and propensity score methods. Each item is crafted to deepen understanding of study selection, bias and confounding control, analysis implications and ethical considerations in clinical research design. Use these MCQs to test comprehension, prepare for exams, and sharpen practical decision-making skills when selecting appropriate designs for pharmaceutical research.

Q1. What is the primary methodological distinction between a randomized controlled trial (RCT) and a quasi-experimental study?

• Presence of a control group
• Use of outcome measures
• Random allocation of participants to study arms
• Prospective data collection

Correct Answer: Random allocation of participants to study arms

Q2. Which observational design is best suited for studying a rare outcome and allows estimation of odds ratios?

• Prospective cohort study
• Cross-sectional study
• Case-control study
• Randomized controlled trial

Correct Answer: Case-control study

Q3. In a cluster randomized trial, what is the primary statistical concern that must be accounted for in sample size calculation?

• Multiple testing correction
• Intracluster correlation (ICC)
• Blinding effectiveness
• Loss to follow-up rate

Correct Answer: Intracluster correlation (ICC)

Q4. Which quasi-experimental design uses a predefined cutoff on an assignment variable to allocate interventions and can approximate causal inference near the threshold?

• Interrupted time-series
• Regression discontinuity design
• Non-equivalent control group design
• Before–after uncontrolled study

Correct Answer: Regression discontinuity design

Q5. Which of the following best describes an interrupted time-series (ITS) design?

• Randomizing individuals to receive intervention or placebo
• Collecting repeated measures over time before and after an intervention to detect level/trend changes
• Matching exposed and unexposed individuals retrospectively
• Conducting a single cross-sectional survey after an intervention

Correct Answer: Collecting repeated measures over time before and after an intervention to detect level/trend changes

Q6. What is the main advantage of a crossover trial compared with a parallel-group RCT?

• Eliminates the need for washout periods
• Each participant serves as their own control, reducing between-subject variability
• Blinding is unnecessary
• Suitable for long-term irreversible outcomes

Correct Answer: Each participant serves as their own control, reducing between-subject variability

Q7. Which bias is especially a concern in observational cohort studies when exposed and unexposed groups differ systematically in prognostic factors?

• Selection bias
• Confounding
• Performance bias
• Detection bias

Correct Answer: Confounding

Q8. What is allocation concealment in randomized trials intended to prevent?

• Participant unblinding after treatment
• Selection/investigator foreknowledge influencing enrollment
• Reporting bias at publication
• Outcome misclassification

Correct Answer: Selection/investigator foreknowledge influencing enrollment

Q9. Which observational design measures exposure and outcome at the same single time point and is useful for estimating prevalence?

• Case-control study
• Prospective cohort study
• Cross-sectional study
• Stepped-wedge trial

Correct Answer: Cross-sectional study

Q10. In a non-equivalent control group quasi-experimental design, what distinguishes it from a randomized trial?

• Outcome measurement is blinded
• Control group is not created by random assignment and may differ at baseline
• Intervention is assigned by a central randomization service
• It always uses longitudinal follow-up for both groups

Correct Answer: Control group is not created by random assignment and may differ at baseline

Q11. Which method is commonly used in observational studies to reduce confounding by measured covariates prior to outcome comparison?

• Intention-to-treat analysis
• Propensity score matching
• Block randomization
• Stratified random sampling

Correct Answer: Propensity score matching

Q12. What is the principal ethical requirement unique to randomized clinical trials compared with many observational studies?

• Obtaining informed consent from participants
• Equipoise — genuine uncertainty about which arm is superior
• Data monitoring for long-term observational registries
• Retrospective chart review approvals

Correct Answer: Equipoise — genuine uncertainty about which arm is superior

Q13. Which design is most appropriate to evaluate the effect of a policy change implemented at a specific date across a population?

• Case-crossover study
• Interrupted time-series analysis
• Cross-sectional survey
• Individual randomized controlled trial

Correct Answer: Interrupted time-series analysis

Q14. In a case-control study nested within a cohort (nested case-control), what is a key advantage?

• Lower cost and more efficient exposure assessment while preserving temporality
• Random allocation of exposure
• Immediate prevalence estimation for the entire cohort
• No need to account for matching in the analysis

Correct Answer: Lower cost and more efficient exposure assessment while preserving temporality

Q15. Which statement about intention-to-treat (ITT) analysis is correct?

• ITT excludes participants who deviate from protocol
• ITT analyzes participants according to the treatment actually received
• ITT preserves randomization benefits by analyzing all randomized participants in assigned groups
• ITT is only appropriate for observational studies

Correct Answer: ITT preserves randomization benefits by analyzing all randomized participants in assigned groups

Q16. A stepped-wedge cluster randomized trial is characterized by which feature?

• All clusters start in the intervention phase simultaneously
• Clusters sequentially cross from control to intervention such that all eventually receive the intervention
• Clusters are randomized but only the control group is analyzed
• It is equivalent to a crossover trial at the individual level

Correct Answer: Clusters sequentially cross from control to intervention such that all eventually receive the intervention

Q17. What is the main limitation of cross-sectional studies when used to infer causal relationships?

• They are very expensive and time-consuming
• They cannot establish temporal sequence between exposure and outcome
• They require randomization
• They always have high loss to follow-up

Correct Answer: They cannot establish temporal sequence between exposure and outcome

Q18. Which observational design is particularly useful to study transient exposures that trigger acute events and uses each subject as their own control?

• Prospective cohort study
• Case-crossover study
• Nested case-control study
• Ecological study

Correct Answer: Case-crossover study

Q19. In assessing external validity (generalizability) of an RCT, which factor is most relevant?

• Precision of the estimate in the trial sample
• Similarity of trial participants and settings to the target population
• Whether allocation concealment was used
• Statistical significance of primary outcome

Correct Answer: Similarity of trial participants and settings to the target population

Q20. Which analytic approach is most appropriate to handle confounding by indication in observational pharmacoepidemiology studies?

• Simple unadjusted comparison of event rates
• Use of instrumental variable analysis or high-quality propensity methods
• Per-protocol analysis ignoring baseline differences
• Cross-sectional correlation analysis

Correct Answer: Use of instrumental variable analysis or high-quality propensity methods

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