This book explains how the formulas and procedures for sample size calculations can be used in a variety of clinical research and development stages. It presents real-world examples from several therapeutic areas to illustrate clinical and statistical concepts, interpretations, and interactions. The book also explores emerging topics in pharmaceutical research and development, including QT/QTc studies with time-dependent replicates and the use of propensity score analysis in nonrandomized or observational studies. This edition now provides sample size calculations for three major areas of clinical research: dose response studies, microarray studies, and Bayesian approaches.