Controls and randomization MCQs With Answer

Introduction: This quiz set on Controls and Randomization is designed for M.Pharm students to strengthen core concepts in experimental design and clinical trial methodology. Understanding controls and randomization is vital to minimize bias, ensure internal validity, and correctly interpret therapeutic effects. These questions go beyond definitions to cover practical issues such as allocation concealment, block and stratified randomization, minimization, types of controls (placebo, active, historical, sham), ethical considerations, and statistical implications like balance, predictability, and handling confounders. Use this focused practice to evaluate your readiness for exams and research planning, and to refine choices you will make when designing robust pharmacological studies.

Q1. What is the primary purpose of using a concurrent control group in a clinical trial?

• To reduce the study duration by using past data
• To provide a contemporaneous comparison that experiences the same external conditions
• To guarantee blinding of participants
• To ensure maximum statistical power regardless of sample size

Correct Answer: To provide a contemporaneous comparison that experiences the same external conditions

Q2. Which randomization method is most appropriate when you need to maintain balance in treatment numbers within small blocks over time?

• Simple randomization
• Block randomization
• Stratified randomization
• Cluster randomization

Correct Answer: Block randomization

Q3. What is allocation concealment intended to prevent?

• Participants guessing their treatment after enrollment
• Investigators predicting the next assignment before enrolling a participant
• Biostatisticians changing the randomization algorithm
• Loss to follow-up in the trial

Correct Answer: Investigators predicting the next assignment before enrolling a participant

Q4. Which control type is most appropriate when withholding an active therapy would be unethical?

• Placebo control
• Historical control
• Active (comparator) control
• Sham control

Correct Answer: Active (comparator) control

Q5. In stratified randomization, strata are formed based on:

• Random number seeds only
• Certain prognostic variables believed to influence outcome
• The sequence of enrollment
• Block sizes exclusively

Correct Answer: Certain prognostic variables believed to influence outcome

Q6. Which statement best describes minimization as a method of allocation?

• It is equivalent to simple randomization with replacement
• It deterministically assigns the next subject to minimize imbalance across chosen covariates, sometimes with a random element
• It uses a fixed block size to ensure unpredictability
• It randomly assigns clusters rather than individuals

Correct Answer: It deterministically assigns the next subject to minimize imbalance across chosen covariates, sometimes with a random element

Q7. Which measure reduces predictability in block randomization?

• Using a fixed small block size
• Using variable block sizes and keeping block lengths concealed
• Implementing open allocation lists
• Assigning treatments alphabetically

Correct Answer: Using variable block sizes and keeping block lengths concealed

Q8. A sham control is most commonly used in which type of study?

• Pharmacokinetic bioequivalence studies
• Surgical or device trials where a procedural placebo is feasible
• Large vaccine field trials
• Historical cohort analyses

Correct Answer: Surgical or device trials where a procedural placebo is feasible

Q9. Which is TRUE about historical controls?

• They eliminate all forms of confounding
• They are derived from previous studies or routine records and may introduce bias due to temporal changes
• They guarantee blinding and allocation concealment
• They always provide a superior level of evidence compared to randomized concurrent controls

Correct Answer: They are derived from previous studies or routine records and may introduce bias due to temporal changes

Q10. What does intention-to-treat (ITT) analysis preserve in randomized trials?

• Original treatment group assignment regardless of adherence, thus preserving randomization
• Only data from participants who completed the protocol per-protocol
• Exclusion of participants with missing outcomes
• Non-random assignment for subgroup analyses

Correct Answer: Original treatment group assignment regardless of adherence, thus preserving randomization

Q11. Which is an advantage of using placebo controls in drug trials?

• They always remove ethical concerns about withholding treatment
• They can help estimate the effect attributable to the active treatment beyond psychological/placebo effects
• They are never subject to regulatory scrutiny
• They ensure perfect external validity across populations

Correct Answer: They can help estimate the effect attributable to the active treatment beyond psychological/placebo effects

Q12. Cluster randomization is primarily used when:

• Individual randomization is simple and preferred
• Interventions are delivered at group level or there is risk of contamination between individuals
• You want to randomize treatments within the same subject simultaneously
• You require equal numbers in each treatment arm regardless of cluster size

Correct Answer: Interventions are delivered at group level or there is risk of contamination between individuals

Q13. Which technique helps control known confounders during design rather than analysis?

• Random digit generation
• Matching subjects on confounding variables
• Post-hoc subgroup analysis
• Using a smaller sample size

Correct Answer: Matching subjects on confounding variables

Q14. What is a potential drawback of simple randomization in small trials?

• It guarantees balance on all prognostic factors
• It may produce substantial imbalance in treatment group sizes or important covariates by chance
• It requires stratification by too many variables
• It always introduces allocation concealment problems

Correct Answer: It may produce substantial imbalance in treatment group sizes or important covariates by chance

Q15. Which randomization method is most suitable when you must ensure balance across multiple prognostic covariates simultaneously?

• Simple randomization without stratification
• Covariate-adaptive randomization (e.g., minimization)
• Using only placebo controls
• Historical controls

Correct Answer: Covariate-adaptive randomization (e.g., minimization)

Q16. Which of the following best describes allocation concealment versus blinding?

• Allocation concealment prevents selection bias before assignment; blinding prevents performance and detection bias after assignment
• They are identical concepts and interchangeable terms
• Blinding is used only in animal studies; allocation concealment only in clinical trials
• Allocation concealment is only needed for baseline measurements

Correct Answer: Allocation concealment prevents selection bias before assignment; blinding prevents performance and detection bias after assignment

Q17. When using block randomization, why should block size be concealed?

• To increase the sample size required
• To prevent investigators from deducing future assignments and introducing selection bias
• To make stratification unnecessary
• To standardize the duration of follow-up

Correct Answer: To prevent investigators from deducing future assignments and introducing selection bias

Q18. What is a key ethical concern when using placebo controls in trials where effective therapy exists?

• Placebos always reduce statistical power
• Withholding established effective therapy may harm participants; placebo use must be justified and minimized
• Placebos remove the need for informed consent
• Placebos guarantee faster regulatory approval

Correct Answer: Withholding established effective therapy may harm participants; placebo use must be justified and minimized

Q19. In a crossover trial, why is a washout period important between treatment periods?

• To increase allocation predictability
• To allow any effects of the first treatment to dissipate and reduce carryover bias
• To randomize clusters rather than individuals
• To avoid the need for blinding

Correct Answer: To allow any effects of the first treatment to dissipate and reduce carryover bias

Q20. Which practice strengthens the credibility of the randomization sequence generation?

• Publishing the sequence before the trial starts without concealment
• Using a reproducible method (e.g., computer-generated random numbers) and documenting the process, while keeping it concealed from recruiters
• Allowing site investigators to choose assignments based on convenience
• Fixing assignments according to calendar dates of enrollment

Correct Answer: Using a reproducible method (e.g., computer-generated random numbers) and documenting the process, while keeping it concealed from recruiters

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