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Re: st: xtlogit, pa questions


From   brendan.halpin@ul.ie (Brendan Halpin)
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: xtlogit, pa questions
Date   Thu, 08 Mar 2012 16:34:22 +0000

On Thu, Mar 08 2012, Kim Peeters wrote:

> Within each cluster the value of the response variable is either
> 0 or 1 for all occasions. This is not due to any design but just because none
> of the participants (one participant = one clusters) in the study experienced a
> transition from one state to the other state (no data or study error).
>
> Both the response variable and the RHS variables are measured
> yearly. The response variable does not vary but recall that this was not done
> by design. The RHS variables do vary for each occasion (i.e. for every year).

Well, it sounds to me that there is no information in your data to
estimate the effect of change in the RHS variables on the outcome, since
the outcome doesn't change. In other words, your data has no
longitudinal value (for this outcome).

It may be that the multiple observations of the RHS variables gives you
a more accurate measurement of those covariates. Your xtlogit/pa model
may well give meaningful cluster-adjusted estimates of the average
effect of these covariates, but I'm not sure. I'd be inclined to fit an
ordinary logit using the average value (across each individual) of the
covariates on the RHS, at least to compare. 

Brendan
-- 
Brendan Halpin,   Department of Sociology,   University of Limerick,   Ireland
Tel: w +353-61-213147  f +353-61-202569  h +353-61-338562;  Room F1-009 x 3147
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