Statistical Power: How to Find the Right Sample Size for Your Next Study

Sample size calculation is a critical component of high-quality clinical research, yet it is frequently absent from studies in the emergency medicine literature. This omission reflects multiple challenges, including uncertainty about how to perform sample size calculations, when they are necessary, and how they influence study validity and interpretation.

At the core of sample size calculation is the concept of statistical power, which is often perceived as complex and inaccessible due to technical language and statistical notation. A clear understanding of statistical power and its relationship to sample size is essential for emergency physicians to critically appraise the rigor, credibility, and impact of clinical research.

This didactic will provide concise, plain-language explanations of key concepts related to statistical power, including type I and type II errors, effect size, and sample size determination. Participants will be introduced to basic methods and commonly used tools for performing sample size calculations, as well as guidance on situations in which such calculations are appropriate or unnecessary. Examples from the emergency medicine literature will be used to illustrate best practices, common pitfalls, and practical application of these principles in research evaluation.