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Re: st: Testing the extent of difference between two coefficients in the same model


From   Maarten Buis <maartenlbuis@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Testing the extent of difference between two coefficients in the same model
Date   Tue, 31 Jan 2012 12:34:22 +0100

On Mon, Jan 30, 2012 at 11:12 PM, David Hoaglin wrote:
>  A model in
> which the two coefficients are equal is the same as the model in which
> the predictor associated with that coefficient is the sum of "old" and
> "new."

This is a trick that is often forgotten (at least in my discipline),
but can have surprisingly useful applications beyond adding linear
constraints to models that do not allow the -constraint- option. I
submitted a Stata tip on this topic a couple of days ago.
<http://www.maartenbuis.nl/wp/sumconstr.html>

-- Maarten

--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany


http://www.maartenbuis.nl
--------------------------
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