ABSTRACT
This chapter discusses sample size determination in clinical trials with implementation in R. It reviews the prerequisites for sample size determination, and presents sample size calculations for the comparison of two-treatment groups for continuous endpoints as well as for the two-treatment comparison for proportions. The chapter investigates sample size and power calculations for clinical trials with time-to-event endpoints. It uses the R library gsDesign to design group sequential trials including sample size calculation and stopping boundaries. The chapter presents design aspects of methods for analysis of clinical trials with time-to-event data, including sample size determination using R function nSurvival in gsDesign Library. It also discusses design and sample size calculation for trials with longitudinal data, and explores an atypical situation in sample size calculation where percent change and coefficient of variation are known. The function nSurvival uses the method described in Lachin and Foulkes.
