Abstract: Objective To explore the differences between the Bayesian interim analysis and the classical interim analysis.
Methods To compare the means of two independent samples between control and treatment, superior hypothesis test was
established. In line with the data requirements for group sequential design, Type I error of Bayesian interim analysis based on
various prior distributions, Power, Average Sample Size and Average Stage were estimated in the interim analysis. Results In
the Pocock and O’ Brien & Fleming designs, the Type I errors in the Bayesian interim analysis based on the skeptical prior
distribution and the handicap prior distribution were controlled at around 0.05. When the powers of these two classical
designs were both 80%, Bayesian powers of the skeptical prior distribution and the handicap prior distribution were markedly
lower. The powers of the non-informative prior distribution and the enthusiastic prior distribution were distinctly higher than
80%. Conclusion In the Bayesian interim analysis based on the skeptical prior distribution and the handicap Prior distribution,
the Type I errors can be well controlled. Bayesian interim analyses using these two prior distributions, compared with the
analysis adopting the O’ Brien & Fleming method, can markedly increase the possibility of ending the clinical trials ahead of
time. The Bayesian interim analyses based on these two distributions do not have practical value for group sequential design
of the Pocock method.