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Re: st: comparing coefficients across 2 models


From   Maarten Buis <maartenlbuis@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: comparing coefficients across 2 models
Date   Tue, 27 Nov 2012 11:48:06 +0100

On Mon, Nov 26, 2012 at 5:43 PM, JVerkuilen (Gmail) wrote:
> I'd even argue that centering categorical predictors is often useful,
> though that's not done as often. This is especially true for variables
> not primarily of substantive interest.

For that I typically prefer what is sometimes called "effect coding",
which means all categories are compared to the grand mean. One example
of a situation where this often makes sense is when your categories
are provinces or states; that way you compare those provinces with the
national average rather than with some arbitrary reference province.
In Stata 12 you can use the -contrasts- command with the -g.- or -gw.-
operators.

-- Maarten

---------------------------------
Maarten L. Buis
WZB
Reichpietschufer 50
10785 Berlin
Germany

http://www.maartenbuis.nl
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