Beta priors determination based on different prior information

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Description

The prior function to calculate the Beta prior parameters

Usage

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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

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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)