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RE: st: Multilevel modelling of survival data


From   "Justin B Echouffo Tcheugui" <jbe24@medschl.cam.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Multilevel modelling of survival data
Date   Tue, 17 Mar 2009 10:20:30 -0000

Dear Marteen,
I appreciate you taking the time.
You are right, but the problem that I have is that by design all
patients in one clinic will belong to the same trial group. As clinics
(not individuals) were allocated either to treatment or control group,
the events in one clinic can only count for one arm of the trial. 
Do you see any other way of dealing with this? 
Many thanks 
Justin B. 

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Maarten buis
Sent: 16 March 2009 21:18
To: stata list
Subject: RE: st: Multilevel modelling of survival data


--- On Mon, 16/3/09, Justin B Echouffo Tcheugui wrote:
> I tried the command stcox with the option -shared () as
> you advised. As you can see below I am not having the
> desired output:
> could not calculate numerical derivatives flat or
> discontinuous region encountered r (430)

One posibility that jumps to mind is: are there any
clinics that only have (valid) observations on either
the treatment or the controll group?

So type:

tab randomgroup clinic, if !missing(_t)

and see if any of the reported counts equal zero.

-- Maarten

-----------------------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


      

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