prior {ph2bye}

Beta priors determination based on different prior information

Description

The prior function to calculate the Beta prior parameters

Usage

prior(type, mu, v, N, W, init)

Arguments

type

type of prior information: "MeanVar" uses mean and variance, "Optimist" uses (ORR) mean, "ORRN" uses ORR and smaple size, "ORRW" uses ORR and CI width.

mu

prior(ORR) mean.

v

prior variance

N

prior sample size.

W

prior confidence interval width.

init

initial value to solve the nonlinear equations for "ORRW" type.

Value

parameters

the vector of Beta parameters: a and b

References

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

Mayo, M. S., & Gajewski, B. J. (2004). Bayesian sample size calculations in phase II clinical trials using informative conjugate priors. Controlled clinical trials 25(2): 157-167.

Tan, S. B., & Machin, D. (2002). Bayesian two-stage designs for phase II clinical trials. Statistics in medicine 21(14): 1991-2012. New York: Wiley.

Examples

prior(type = "MeanVar", mu=0.2, v=0.025)
prior(type = "Optimist", mu = 0.2)
prior(type = "ORRN", mu = 0.2, N = 10)
prior(type = "ORRW", mu = 0.2, W = 0.5)