Statalist


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: st: RE: sample size estimation for cox model


From   moleps islon <moleps2@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: sample size estimation for cox model
Date   Wed, 16 Sep 2009 07:28:32 +0200

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 <Kieran.McCaul@uwa.edu.au> 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: 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
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
>
>
>
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
>

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index