plan.GST {AGSDest}R Documentation

Plans a group sequential trial (GST)

Description

Plans a group sequential trial (GST)

Usage

plan.GST(K, t = (1:K)/K, Imax=NULL, SF, phi, alpha, delta=NULL, pow=NULL, compute.alab = TRUE, compute.als = TRUE)

Arguments

K number of stages
t vector with the cumulative information fraction (default: (1:K)/K)
Imax maximum information number (default: NULL)
SF spending function (for details see below)
phi parameter of spending function when SF=3 or 4 (See below)
alpha alpha (type I error rate)
delta effect size (alternative)(default: NULL)
pow power (default: NULL)
compute.alab specify if alpha-absorbing parameter values should be calculated (default: TRUE)
compute.als specify if alpha-values ''spent'' at every stage should be calculated (default: TRUE)

Details

The user has to specify either Imax or delta and pow. If all three items are specified, the pre-defined maximum information number is newly calculated from the information for delta and power, and Imax is overwritten.

SF defines the spending function.
SF = 1 O'Brien and Fleming type spending function of Lan and DeMets (1983)
SF = 2 Pocock type spending function of Lan and DeMets (1983)
SF = 3 Power family (c_α* t^phi); phi must be greater than 0
SF = 4 Hwang-Shih-DeCani family; (1-e^{-phi t})/(1-e^{-phi}), where phi cannot be 0

Value

plan.GST returns an object of the class GSTobj. An object of class GSTobj is a list containing the following components:

K number of stages
a lower critical bounds of group sequential design (are currently always set to -8)
b upper critical bounds of group sequential design
t vector with cumulative information fraction
al alpha (type I error rate)
SF spending function
phi parameter of spending function when SF=3 or 4 (See below)
Imax maximum information number
delta effect size used for planning the primary trial

Author(s)

Niklas Hack niklas.hack@meduniwien.ac.at and Werner Brannath werner.brannath@meduniwien.ac.at

References

Brannath, W, Mehta, CR, Posch, M (2008) ''Exact confidence bounds following adaptive group sequential tests'', Biometrics accepted.

See Also

GSTobj, print.GSTobj, plot.GSTobj

Examples

##The following plans an O'Brien and Flaming group sequential design (GSD) 
##with 4 stages and equally spaced looks.

pT=plan.GST(K=4,SF=1,phi=0,alpha=0.025,delta=6,pow=0.8,compute.alab=TRUE,compute.als=TRUE)

[Package AGSDest version 1.0 Index]