Investigating started sample size, completed sample size and drop‐out rate in 10 252 phase III clinical trials: Insights from ClinicalTrials.gov

Our findings indicate that a majority of the analysed trials lack sufficient statistical power (80%) to detect small effect sizes, and approximately half of the trials did not have 80% power to detect medium effect sizes. Notably, trials funded by NIH/US Fed exhibit significantly smaller sample sizes compared to trials sponsored by industry. When conducting sample size calculations for clinical trials, it is crucial to consider the anticipated effect size, variability and drop-out rate.