CCDM Statistical Analysis 2 — Questions and Answers
Question 1: In a clinical trial, a p-value of 0.03 is obtained. Which statement is most accurate?
- The probability that the null hypothesis is true is 3%
- There is a 3% chance of observing results as extreme as these if the null hypothesis is true (Correct answer)
- The treatment effect is clinically meaningful
- The study has 97% power to detect the effect
Correct answer: There is a 3% chance of observing results as extreme as these if the null hypothesis is true
A p-value represents the probability of obtaining results at least as extreme as observed, assuming the null hypothesis is true.
Question 2: Which type of analysis includes all randomized patients in their originally assigned treatment groups, regardless of protocol adherence?
- Per-protocol analysis
- Intention-to-treat analysis (Correct answer)
- Completer analysis
- On-treatment analysis
Correct answer: Intention-to-treat analysis
Intention-to-treat (ITT) analysis includes all randomized subjects analyzed in their assigned groups, preserving randomization balance.
Question 3: A 95% confidence interval for a mean difference is (2.1, 8.4). What does this indicate?
- There is a 95% probability the true mean lies in this range
- 95% of individual observations fall in this range
- We are 95% confident the true population parameter lies within this interval (Correct answer)
- The p-value is exactly 0.05
Correct answer: We are 95% confident the true population parameter lies within this interval
A confidence interval means that 95% of similarly constructed intervals from repeated sampling would contain the true population parameter.
Question 4: When is a Kaplan-Meier curve the most appropriate analytical tool?
- Comparing proportions between two groups
- Analyzing time-to-event data with censored observations (Correct answer)
- Measuring correlation between two continuous variables
- Comparing means across three or more groups
Correct answer: Analyzing time-to-event data with censored observations
Kaplan-Meier curves are used to estimate survival functions from time-to-event data that includes censored observations.
Question 5: What does a hazard ratio of 0.70 indicate in a survival analysis?
- The treatment group has a 30% lower risk of the event at any point in time (Correct answer)
- 70% of patients in the treatment group survived
- The treatment reduces absolute risk by 70%
- Patients in the control group survive 0.70 times longer
Correct answer: The treatment group has a 30% lower risk of the event at any point in time
A hazard ratio of 0.70 means the treatment group experiences the event at 70% the rate of the control group, a 30% relative reduction.
Question 6: Which statistical method is used to adjust for multiple baseline covariates simultaneously while estimating a treatment effect?
- Chi-square test
- Paired t-test
- Analysis of covariance (ANCOVA) (Correct answer)
- Fisher's exact test
Correct answer: Analysis of covariance (ANCOVA)
ANCOVA adjusts for baseline covariates to reduce residual variance and provide a more precise estimate of the treatment effect.
Question 7: In a crossover trial, what statistical test is most appropriate when comparing two continuous outcomes with normally distributed data?
- Independent samples t-test
- Mann-Whitney U test
- Paired t-test (Correct answer)
- Log-rank test
Correct answer: Paired t-test
In crossover designs, the same subjects receive both treatments, making paired analyses appropriate to account for within-subject correlation.
CCDM Statistical Analysis 2
In a clinical trial, a p-value of 0.03 is obtained.
Which statement is most accurate?