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Re: st: standard error for estimated risk difference from logit model


From   Joseph Coveney <jcoveney@bigplanet.com>
To   Statalist <statalist@hsphsun2.harvard.edu>
Subject   Re: st: standard error for estimated risk difference from logit model
Date   Fri, 04 Mar 2005 13:12:10 +0900

Tim Wade wrote:

I have estimated probabilities for two groups (e.g., exposed and
unexposed)  using the "adjust" command after a logistic regression,
holding several other covariates to their mean or other specified
values. The main exposure varies among individuals and is continuous.
I would like to estimate the risk difference for these each individual
(p_exposed-p_unexposed) and the  confidence limit for this estimate.
P_unexposed is constant for all unexposed. The risk difference is no
problem, simply p_exposed-p_unexposed but I can't  figure out how to
get the confidence limits or standard error. A partial line listing of
the predicted values follows, xse is the standard error of the linear
predictor (not of the probability). The only other option I could
think of would be to manually input the mean and other values get the
estimates and their ci's using predictnl. Does anyone have any other
suggestions?

----------------------------------------------------------------------------

Why not get them directly by changing the link function?

Currently:  -glm . . . , family(binomial) link(logit)-

Recommendation:  -glm . . . , family(binomial) link(identity)-

Joseph Coveney





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