ACRP ACRP Biostatistics and Data Analysis 2 — Questions and Answers
Question 1: What is the role of a Data Safety Monitoring Board (DSMB) in a clinical trial?
- To audit site financials
- To independently monitor accumulating data and recommend stopping or modifying the trial if safety or efficacy criteria are met (Correct answer)
- To manage data entry errors
- To review informed consent language
Correct answer: To independently monitor accumulating data and recommend stopping or modifying the trial if safety or efficacy criteria are met
A DSMB is an independent committee that periodically reviews unblinded interim data to protect participant safety and ensure trial integrity.
Question 2: What is a Type I error in statistical testing?
- Failing to detect a true treatment effect
- Concluding that a treatment is effective when it is not (false positive) (Correct answer)
- A data entry mistake in the CRF
- An error in the randomization scheme
Correct answer: Concluding that a treatment is effective when it is not (false positive)
A Type I error (alpha error) occurs when the null hypothesis is rejected incorrectly, falsely concluding that an ineffective treatment works.
Question 3: What is stratified randomization and when is it used?
- Randomization performed in layers based on site geography only
- Randomization that ensures balance of key prognostic factors (e.g., age, disease severity) across treatment groups (Correct answer)
- Randomization using sealed envelopes only
- Sequential assignment based on enrollment order
Correct answer: Randomization that ensures balance of key prognostic factors (e.g., age, disease severity) across treatment groups
Stratified randomization controls for important baseline variables by ensuring they are equally distributed between treatment arms, improving comparability.
Question 4: What is the primary purpose of a statistical analysis plan (SAP) in a clinical trial?
- To describe the budget for statistical consultants
- To pre-specify all statistical methods and analyses before data unblinding to prevent bias (Correct answer)
- To summarize final study results for publication
- To outline data entry procedures
Correct answer: To pre-specify all statistical methods and analyses before data unblinding to prevent bias
The SAP documents all planned analyses before unblinding, ensuring results are not influenced by knowledge of outcome data (post-hoc analysis bias).
Question 5: What does 'multiplicity' refer to in clinical trial statistics?
- Multiple sites conducting the same study
- The inflation of the Type I error rate when performing multiple statistical tests (Correct answer)
- Multiple treatment arms in one study
- Running the same analysis using different software
Correct answer: The inflation of the Type I error rate when performing multiple statistical tests
When multiple endpoints or comparisons are tested, the probability of at least one false positive increases; multiplicity adjustments (e.g., Bonferroni) control this inflation.
Question 6: What is the Kaplan-Meier method used for in clinical research?
- Comparing laboratory values between groups
- Estimating survival or time-to-event probabilities from censored data (Correct answer)
- Calculating drug plasma concentrations
- Randomizing participants to treatment groups
Correct answer: Estimating survival or time-to-event probabilities from censored data
The Kaplan-Meier method produces survival curves that estimate the probability of an event (e.g., death, relapse) over time, accounting for participants who leave the study early.
ACRP ACRP Biostatistics and Data Analysis 2
What is the role of a Data Safety Monitoring Board (DSMB) in a clinical trial?