postprob {ph2bayes}

The posterior probability criterion function

Description

Thall and Simon's criterion function for determining the trial decision cutoffs based on the posterior probability.

Usage

postprob(y, n, alpha_e, beta_e, alpha_s, beta_s, delta)

Arguments

y

the number of responses among n patients treated by the experimental drug at a certain stage of the trial.

n

the number of patients treated by the experimental drug at a certain stage of the trial.

alpha_e

the hyperparameter (shape1) of the Beta prior for the experimental drug.

beta_e

the hyperparameter (shape2) of the Beta prior for the experimental drug.

alpha_s

the hyperparameter (shape1) of the Beta prior for the standard drug.

beta_s

the hyperparameter (shape2) of the Beta prior for the standard drug.

delta

the minimally acceptable increment of the response rate for the experimental drug compared with the standard drug.

Value

prob

the posterior probability: \Pr(p_E > p_S + \delta | y)

References

Thall, P. F., Simon, R. (1994). Practical Bayesian guidelines for phase IIB clinical trials. Biometrics 50: 337-349.

Yin, G. (2012). Clinical Trial Design: Bayesian and Frequentist Adaptive Methods. New York: Wiley.