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Re: st: Using xtgee with multiple weights per ID
-xtgee- is obviously the wrong tool. Try -gllamm-. Time points will
be "level 1" units and you can specify -pweights- for them.
-Steve
On Nov 26, 2008, at 3:02 PM, Ariel Linden, DrPH wrote:
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.
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