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st: RE: sample size estimation for cox model


From   "Kieran McCaul" <Kieran.McCaul@uwa.edu.au>
To   <statalist@hsphsun2.harvard.edu>
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
email: Kieran.McCaul@uwa.edu.au
http://myprofile.cos.com/mccaul 
http://www.researcherid.com/rid/B-8751-2008
______________________________________________
If you live to be one hundred, you've got it made.
Very few people die past that age - George Burns

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of moleps islon
Sent: Wednesday, 16 September 2009 4:04 AM
To: statalist@hsphsun2.harvard.edu
Subject: st: sample size estimation for cox model

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

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

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

regards,

M
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