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st: Re: Prediction after xtgee
From
"Joseph Coveney" <[email protected]>
To
<[email protected]>
Subject
st: Re: Prediction after xtgee
Date
Mon, 19 Jul 2010 16:22:43 +0900
Terry Lum wrote:
I ran a xtgee regression, with a list of chronic illnesses as right hand
side variables, together which a few demographic and health insurance
variables. The dependent variable is health care cost. I want to see how
each chronic illness affect the costs, after controlling for demographic
and insurance variables.
I generated the predicted value of the cost variable and summarize the
predict costs by chronic illness. It seems that this may not be the correct
way to do so. It seems that they may not be the right way to do so. I
should set all chronic illness variable to zero except the targeted one. I
tried to use the following comment
predict newvar if chronic1==1 & chronic2==0 $ chronic3==0...... &e(sample)
But it seems that by using this comment, STATA only predicted the costs for
those observation with chronic==1.
Please suggest the corrected way to generate predicted cost for each
chronic illness.
--------------------------------------------------------------------------------
-margins- might provide a better approach. Something like
xtset . . .
xtgee medical_cost i.chronic_illness c.demographic_variable_1 . . . ///
c.insurance_variable_1 . . ., family(igaussian) corr(independent) robust
margins i.chronic_illness, post
See its help-file for more options, e.g., setting covariates to specific
values, and accessing the prediction vector and covariance matrix for forming
contrasts and the like.
Joseph Coveney
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