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st: sample size calculation for survival data


From   "Di Stefano, Paola" <paola.di.stefano@medtronic.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: sample size calculation for survival data
Date   Tue, 6 Mar 2007 18:06:56 +0100

Dear all,

Does anybody know how to calculate sample size in the following
situation with Stata?

H0: s1=s2 (survival at 2 years) H1: one side (logrank non paramentric
test for exponential data)
Size ratio =1
S1=77,5%, s2=83,125%
Alfa=5%
Beta=20%
Lost follow-up 10% per year
Accrual time =2 years
Total study time =4 years (2 enrollment+2 follow-up)

I would like to perform this analysis with Stata but the manual doesn't
describe it.
Could you help me please?
Thanks a lot
Paola



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