RE: Centering (was Re: Missing covariates)
From: "Gibiansky, Leonid" <gibianskyl@globomax.com>
Subject: RE: Centering (was Re: Missing covariates)
Date: Mon, 30 Jul 2001 17:47:27 -0400
I am not sure whether Leonid quoted here is me. If yes, I did not propose
centering of the categorical covariates, including gender. I think this is
not very useful. I think that for continuous covariates we implicitly assume
reasonable distribution (normal or smooth or just not very weird) around the
mean or median. For categorical, the distribution degenerates into
delta-functions and any centering becomes questionable. I still cannot
understand why one may need to reduce covariate model to the base one. From
the covariate model one can extract information about any typical person,
with their particular characteristics: gender, color of eyes, weight, etc.
If one needs prediction for a typical person, one may define this typical
person via typical age, weight. You cannot define typical gender, there is
no way to do it !
Leonid Gibiansky
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