Effects of violations of prerequisites in sequential triangular designs Available to Purchase

Testing group differences in sequential designs is based on critical values of the standard normal distribution. This approximation is not called into question in various variants if sequential tests. It is the basis not only for assessment of the null hypothesis but also for calculating sample size and power. Additional assumption concerning this kind of tests are homogeneity of variances and normal distributed random variables. In a simulation study effects of using the α-percentile of the standard normal distribution and of violating various prerequisites on type I error rate and power are evaluated. Although the focus lies on triangular tests based on Whiteheads method [1] for continuous monitoring other sequential designs like the group sequential test of OBrien-Fleming [2] and Pocock [3] were also taken into consideration.