Statalist


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

st: Using xtgee with multiple weights per ID


From   "Ariel Linden, DrPH" <alinden@lindenconsulting.org>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Using xtgee with multiple weights per ID
Date   Wed, 26 Nov 2008 12:02:01 -0800

Hi All,

 

I am trying to run a weighted xtgee using different weights per each
person/period. This model is based on the work of Hernan et al., (estimating
the causal effect of zidovudine on CD4 count with a marginal structural
model for repeated measures, stats in med 2002). Conceptually each
person/period will have a weight based on the propensity of getting the
treatment at that office visit, conditional on time varying covariates from
past visits.

 

However, when I run the xtgee using the weights, I get an error message
stating "weight must be constant within ID".  In addition, the model is
tossing out the interaction variable for "change: treatment * time because
of colinearity. This doesn't get tossed out when I use an unweighted model.

 

Any help would be appreciated!

 

Ariel

 

 

 


*
*   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