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Re: st: graphs - help


From   rgutierrez@stata.com (Roberto G. Gutierrez, StataCorp.)
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: graphs - help
Date   Mon, 24 Feb 2003 10:08:09 -0600

In response to my earlier reply about graphing comparitive baseline hazards
(one frailty, one non-frailty), Eldira <Gjoncae@aol.com> now asks:

> Many thanks for your help. It works well now but I have another question.
> You add the option alpha1 when predictiong the hazard after running the
> model with heterogeneity- predict h_frailty, hazard alpha1. Does that mean
> that you assume shared frailty?

No, I do not assume shared frailty in the model.  Using the -alpha1- option
when -predict-ing gives estimates of the conditional (or individual) predicted
quantity, in this case, the hazard.  If you do fit a shared frailty model,
-alpha1- becomes the default to -predict-, but you do not have to assume
shared frailty to use -alpha1-.

> In my data, I have no reason to believe that there is shared frailty. Should
> I use alpha1, unconditional or no option at all?

It depends (see my earlier post).  If you want to compare individual hazards
use -alpha1-.  Use -unconditional- to compare population hazards.

--Bobby
rgutierrez@stata.com
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