OE Journal

ORIGINAL ANALYSIS

Did the Study Recruit Enough Patients? The 3 Things You Need to Know to Calculate A Sample Size

Sample size decisions shape how confidently trial results can be interpreted, and understanding these calculations helps clarify whether a study is truly equipped to detect meaningful differences. The process hinges on three elements: an acceptable false-positive risk, the probability of detecting a true effect, and the expected treatment difference that matters clinically. Adjustments are often added to account for dropouts. Changing any of these assumptions can dramatically shift the required sample size—larger effects need fewer patients, while higher power demands more. Reviewing these components makes it easier to judge whether a trial is adequately powered or potentially misleading.