Finding extended power-family group-sequential designs

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Description

powerfamily is used to find a one-sided extended power-family group-sequential design

Usage

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powerfamily(futility = 0, efficacy = 0, delta0 = 0, delta1 = 1/3,
    J = 2, sigma = 1, sd.known = TRUE, alpha = 0.05, power = 0.9)

Arguments

futility

shape parameter for futility boundaries (default: 0)

efficacy

shape parameter for efficacy boundaries (default: 0)

delta0

mean difference in treatment effect under the null hypothesis (default: 0)

delta1

clinically relevant difference used to power the trial (default: 1/3)

J

number of stages in the trial (default: 2)

sigma

assumed standard deviation of treatment responses (default: 1)

sd.known

logical value indicating if sigma will be treated as known; if FALSE, a quantile substitution method will be used to modify the stopping boundaries (default TRUE)

alpha

one-sided type-I error rate required (default: 0.05)

power

power required (default: 0.9)

Details

powerfamily uses the extended power-family of group-sequential tests. A description of the extended power-family is provided in Wason (2012).

Value

groupsize

the number of patients required per arm, per stage

futility

the futility boundaries for the design

efficacy

the efficacy boundaries for the design

ess

the expected sample size at the delta0; the expected sample size at the delta1; and the maximum expected sample size

typeIerror

the actual type-I error rate of the design

power

the actual power of the design

References

Wason, J.M.S. OptGS: an R package for finding near-optimal group-sequential designs. Journal of Statistical Software, 66(2), 1-13. http://www.jstatsoft.org/v66/i02/

Examples

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##Find a three-stage design that has shape parameters -0.5 and 0.5.
threestagedesign=powerfamily(J=3,futility=-0.5,efficacy=0.5) 
plot(threestagedesign)