AGSDest (version 2.3.4)

plan.GST: 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)

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)

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

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 (\(c_\alpha* t^\phi\)); phi must be greater than 0
SF =	4 Hwang-Shih-DeCani family; \((1-e^{-\phi t})/(1-e^{-\phi})\), where phi cannot be 0

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

# NOT RUN {
##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)
# }