...
Well if the calculation is post hoc, then you already know what the hazard ratio and the number of events are and that's all you need to calculate the power.
______________________________________________
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: [email protected]
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: [email protected] [mailto:[email protected]] On Behalf Of moleps islon
Sent: Wednesday, 16 September 2009 1:29 PM
To: [email protected]
Subject: Re: st: RE: sample size estimation for cox model
Yes, I´m trying to do a post-hoc power calculation (for what its
worth). However I´m uncertain as to the SD. The covariate is binary
and using the SD of the covariate itself yields an SD of only 0.2..
M
On Wed, Sep 16, 2009 at 1:15 AM, Kieran McCaul <[email protected]> wrote:
> ...
>
> 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: [email protected]
> 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: [email protected]
> [mailto:[email protected]] On Behalf Of moleps islon
> Sent: Wednesday, 16 September 2009 4:04 AM
> To: [email protected]
> 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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