Power and Sample Size

Abstract

A critical component of clinical trial design is determining the appropriate sample size. Because clinical trials are planned in advance and require substantial resources per patient, the number of patients to be enrolled can be selected to ensure that enough patients are enrolled to adequately address the research objectives and that unnecessary resources are not spent by enrolling too many patients. The most common approach for determining the optimal sample size in clinical trials is power calculation. Approaches for power calculations depend on trial characteristics, including the type of outcome measure and the number of treatment groups. Practical considerations such as trial budget, accrual rates, and drop-out rates also affect the study team’s plan for determining the planned sample size for a trial. These aspects of sample size determination are discussed in addition.