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st: RE: sample size estimation for cox model

From   "Kieran McCaul" <>
To   <>
Subject   st: RE: sample size estimation for cox model
Date   Wed, 16 Sep 2009 07:15:05 +0800


I haven't used stpower before but it seems to want the SD of the
covariate.  The diagonal of variance-covariance matrix, e(V), contains
the variance of the estimated betas, which is not the same thing.

Are you doing a post-hoc power calculation?

Kieran McCaul MPH PhD
WA Centre for Health & Ageing (M573)
University of Western Australia
Level 6, Ainslie House
48 Murray St
Perth 6000
Phone: (08) 9224-2701
Fax: (08) 9224 8009
If you live to be one hundred, you've got it made.
Very few people die past that age - George Burns

-----Original Message-----
[] On Behalf Of moleps islon
Sent: Wednesday, 16 September 2009 4:04 AM
Subject: st: sample size estimation for cox model

Dear listers,
How do I determine standard deviation (sd) for survival data in a cox

Is it correct to just use y=sqrt of e(V) and plug it into

stpower cox, hratio(x) sd(y) ??


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