SEQUENTIAL-METHODS BASED ON THE BOUNDARIES APPROACH FOR THE CLINICAL COMPARISON OF SURVIVAL TIMES

The earliest formal sequential procedure, the sequential probability r atio test, involved the plotting of certain test statistics and compar ison with straight line parallel boundaries. The boundaries approach c an now be used with a wide variety of test statistics, including those appropriate to the analysis of survival data. The boundaries can take various forms, although the use of straight lines still eases the und erlying mathematical theory while at least approximating to the requir ements of the majority of clinical trials. The implementation of seque ntial methods needs to be made flexibly and sensitively, with each cli nical trial meriting an individualized approach.