CPI Data Collection & Analysis Techniques 2 — Questions and Answers
Question 1: In a clinical trial, what is the primary purpose of using a double-blind design when collecting outcome data?
- To reduce sample size requirements
- To eliminate bias from both participant and assessor expectations (Correct answer)
- To simplify the randomization process
- To ensure all participants receive active treatment
Correct answer: To eliminate bias from both participant and assessor expectations
Double-blind design prevents both participants and outcome assessors from knowing treatment assignment, minimizing performance and detection bias.
Question 2: Which statistical method is most appropriate for analyzing time-to-event data in a clinical trial comparing two treatment arms?
- Linear regression
- Chi-square test
- Kaplan-Meier survival analysis with log-rank test (Correct answer)
- Pearson correlation coefficient
Correct answer: Kaplan-Meier survival analysis with log-rank test
Kaplan-Meier survival analysis with the log-rank test is the standard approach for comparing time-to-event outcomes between treatment groups.
Question 3: A physician investigator notices that laboratory values collected at one site are consistently 10% higher than other sites. This is an example of:
- Random error
- Systematic bias (Correct answer)
- Sampling variability
- Type II error
Correct answer: Systematic bias
Consistent directional differences across a site indicate systematic bias, often due to equipment calibration or procedural differences.
Question 4: What does the term 'imputation' refer to in clinical trial data analysis?
- Removing outlier data points from the dataset
- Assigning values to missing data using statistical methods (Correct answer)
- Converting continuous variables to categorical
- Recalculating endpoints after database lock
Correct answer: Assigning values to missing data using statistical methods
Imputation is the process of substituting estimated values for missing data to maintain dataset completeness and reduce bias.
Question 5: Under ICH E6(R2) GCP guidelines, how long must essential trial documents generally be retained after completion of the trial?
- 2 years
- 5 years
- At least 2 years after the last marketing approval or 2 years after formal discontinuation (Correct answer)
- Until the sponsor's discretion
Correct answer: At least 2 years after the last marketing approval or 2 years after formal discontinuation
ICH E6(R2) requires retention of essential documents for at least 2 years after the last approval or 2 years after formal discontinuation, though local regulations may require longer.
Question 6: Which of the following best describes an 'interim analysis' in a clinical trial?
- Analysis performed after all data are collected and the database is locked
- A pre-specified analysis of accumulating data before trial completion (Correct answer)
- A post-hoc subgroup analysis requested by regulators
- A sensitivity analysis performed to check assumptions
Correct answer: A pre-specified analysis of accumulating data before trial completion
An interim analysis is a pre-specified examination of accumulating data during a trial, often used for safety monitoring or adaptive design decisions.
Question 7: When a CRF field is left blank and no data were collected, what is the most appropriate action for the investigator?
- Leave it blank and move on
- Enter 'N/A' without documentation
- Document the reason for missing data according to protocol and sponsor instructions (Correct answer)
- Estimate the value based on previous visits
Correct answer: Document the reason for missing data according to protocol and sponsor instructions
Missing data must be documented with the reason according to protocol requirements; fabricating or estimating values without a pre-specified method is a GCP violation.
CPI Data Collection & Analysis Techniques 2
In a clinical trial, what is the primary purpose of using a double-blind design when collecting outcome data?