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Re: Corrected repost: Two general questions about xt commmands and re / fe


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: Corrected repost: Two general questions about xt commmands and re / fe
Date   Sat, 11 Apr 2009 23:51:32 +0200

<>

BTW, just out of curiosity: Your problem sounds very much like a survival analysis issue. Have you considered -stset-ting?


HTH
Martin
_______________________
----- Original Message ----- From: "Mark Marshall" <mrmarsh@woosh.co.nz>
To: <statalist@hsphsun2.harvard.edu>
Sent: Saturday, April 11, 2009 11:37 PM
Subject: Corrected repost: Two general questions about xt commmands and re / fe


Hi

I am using Stata 9.2 on windows.

I am fitting an xtpoisson model to unbalanced panel data (n counts of death over T months), with a grouping variable called unit that signifies the ICU
where the data come from. E.g

obs_rrt T unit
0 5 4
3 6 4
2 7 4
4 8 4
3 9 4
1 10 4
3 2 3
1 3 3
1 4 3
1 5 3
0 6 3
1 7 3

Question 1.

When I specify

tis T

my understanding is that this does not explicitly model T in the model (I
want to model the death rate in relationship to time, amongst other things),
and I would have to specify T in the command line to do this. Is this
correct?

Question 2.

I would like to specify T and some other exposure covariates as fixed
effects, and unit as a random effect in the model. If I specify all of these
as independent variables in the command line, and then use the re option,
how can I tell which is modelled as fixed, and which is modelled as random?

Thanks,

Mark Marshall









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