PWEALL (version 1.3.0.1)

cpboundary: The stopping boundary based on the conditional power criteria

Description

This will calculate the stopping boundary based on the conditional power criteria, i.e. if observed HR is above the boundary, the conditional power will be lower than the designated level. All the calculation is based on the proportional hazards assumption and the Cox model.

Usage

cpboundary(Dplan=300,alpha=0.05,two.sided=1,pi1=0.5,cpcut=c(0.2,0.3,0.4),
            BetaD=log(0.8),Beta0=log(1),prop=seq(0.1,0.9,by=0.1))

Value

CPTbound

Boundary based on the conditional power under current trend

CPNbound

Boundary based on the conditional power under null hypothesis

CPDbound

Boundary based on the conditional power according to design, i.e. under alternative hypothesis

Arguments

Dplan

Planned number of events at study end

alpha

Type 1 error rate

two.sided

=1 two-sided test and =0 one-sided test

pi1

Allocation probability for the treatment group

cpcut

the designated conditional power level

BetaD

designed log hazard ratio, i.e. under alternative hypothesis

Beta0

null log hazard ratio, i.e. under null hypothesis

prop

proportion of Dplan observed

Author

Xiaodong Luo

Details

This will calculate the stopping boundary based on the conditional power criteria, i.e. if observed HR is above the boundary, the conditional power will be lower than the designated level. All the calculation is based on the proportional hazards assumption and the Cox model.

References

Halperin, Lan, Ware, Johnson and DeMets (1982). Controlled Clinical Trials.

See Also

cp,cpstop

Examples

###Calculate the stopping boundary at 10-90 percent of the target 300 events 
###when the condition power are c(0.2,0.3,0.4) with 
###2:1 allocation ratio between the treatment group and the control group
cpboundary(pi1=2/3)