ABSTRACT
The alpha-spending function approach of the classical group sequential design is especially useful in providing a flexible tool for monitoring the safety and efficacy aspects of clinical trials. Particularly, this approach provides flexibility in the schedule and the number of interim analyses. Adaptive sample size design, also known as SSR, is one of the most popular forms of adaptive design for the clinical trials. To protect the integrity of an ongoing trial, the concealment of the treatment group assignment is best kept intact. An alternative correction strategy uses the mean squared error of a regression model with some baseline covariate other than the treatment group. However, when considering sample size for the second stage, there will be a maximum resource-allowable sample size, n2max for consideration, but that is also a business matter and needs not be decided in the protocol.
