ABSTRACT
This chapter discusses the regulatory requirement regarding the role of sample size calculation in clinical research. It provides some basic considerations for sample size calculation. These basic considerations include study objectives, design, hypotheses, primary study endpoint, and clinically meaningful difference. The chapter describes the concepts of type I and type II errors and procedures for sample size calculation based on precision analysis, power analysis, probability assessment, and reproducibility probability. In practice, it is often of interest to determine whether a clinical trial that produced positive clinical results provides substantial evidence to assure reproducibility and generalizability of the clinical results. In clinical research, commonly considered hypotheses include point hypotheses for testing equality and interval hypothesis for testing equivalence/noninferiority and superiority. In clinical trials, it is desirable to perform a sample size reestimation based on clinical data accumulated up to the time point.
