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Re: st: Xtgee - noconstant option


From   Maarten Buis <maartenlbuis@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Xtgee - noconstant option
Date   Thu, 22 Mar 2012 15:13:10 +0100

On Thu, Mar 22, 2012 at 2:44 PM, Solon Moreira wrote:
> I'm trying to run an xtgee model predicting firm's market-share on t+1 using a group of explanatory variables regarding firm characteristics (continuous) and contractual aspects of technology transfer contracts (dummy). I am using the following specifications: link (identity) family (Gaussian) corr (exchangeable). My issue here is related with the fact that when I set the option noconstant (go through the origin) all the coefficients become much more significant. Although I would expect that for some variables it makes sense, I do not fully understand this effect as well if it is right to use in that option for an xtgee model. Would someone have a suggestion if the use of noconstant is not indicated in this case?

Including a constant when you should not do so is a lot less serious
than excluding a constant when you should not do so. So, including the
constant is the safe thing to do. This is true in general, but
especially with -xt- models.

Hope this helps,
Maarten

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


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

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