Conditional power calculation for the difference of proportions

[AudreyM]

Hello,

i need to perform a futility analysis where the hypothesis of testing are:

The null hypothesis H0:                      Rc-Ra ≤ -10

The alternative hypothesis H1:           Rc-Ra > -10

where Rc and Ra are the response rate of treatments C and A respectively.

At the end of the study Nc = 450, Na = 300 subjects.

where Nc and Na are the number of subjects planned to be randomised in treatments C and A respectively.

At futility analysis time, i have Nc = 215, Na = 143 subjects and Rc=0.703 and Ra=0.618

i need to calculate the conditional power at time of futility analysis.

i looked into SAS support but i am not really clear what procedure is the most appropriate and the SAS codes/options.

thanks for your help.

[SteveDenham]

I would think that PROC POWER for comparison of two binomials and some additional options ought to work.  Check the examples in the documentation.

SteveDenham