ACRP Biostatistics and Data Analysis Flashcards

What is the purpose of calculating sample size before initiating a clinical trial?

Answer: To ensure the study has sufficient statistical power to detect a clinically meaningful difference

Sample size calculations ensure the trial is adequately powered to detect the pre-specified effect size with acceptable type I and type II error rates.

What does 'statistical power' mean in a clinical trial?

Answer: The probability of correctly rejecting a false null hypothesis

Statistical power (1 − β) is the probability that a study will detect a true treatment effect when one actually exists.

What is a p-value in the context of clinical trial results?

Answer: The probability of observing results as extreme as those found, assuming the null hypothesis is true

A p-value quantifies how likely the observed data would occur by chance if the null hypothesis were true; it does not measure effect size or clinical significance.

What is the difference between per-protocol (PP) and intent-to-treat (ITT) analysis in clinical trials?

Answer: ITT includes all randomized participants regardless of compliance; PP includes only those who completed per protocol

ITT preserves randomization by analyzing all participants as randomized, while PP analysis is restricted to those who adhered to the protocol, which may introduce bias.

What is randomization in clinical trials and why is it important?

Answer: Randomly assigning participants to treatment groups to eliminate selection bias and balance confounders

Randomization distributes known and unknown confounding variables equally across treatment groups, ensuring valid comparison of outcomes.

What is a confidence interval (CI) and how is it interpreted in clinical trial results?

Answer: A range of values within which the true population parameter is estimated to lie with a specified probability

A 95% CI means that if the study were repeated 100 times, the true effect would fall within the calculated interval approximately 95 times.