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Re: st: interaction effect in logit model with orthogonal predictors (-inteff-)


From   Johannes Geyer <JGeyer@diw.de>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: interaction effect in logit model with orthogonal predictors (-inteff-)
Date   Thu, 13 Mar 2008 13:47:25 +0100

Eva wrote:
... However, this means that for each observation, cat1 is set to 1 for
some of the computations, leaving the values of cat2 and cat3
unchanged. But it is impossible for an observation to have cat1=1 and
cat2=1 at the same time. The interaction effects for these
observations seem rather hypothetical to me.

***

I agree with you. The problem occurs always with dummies for different 
categories. I had the same problem but could use -margeff- which has an 
option -dummies- that enables to take into account dummies from 
categorical variables (you can do similar things with -mfx- and option 
-at()-. Unfortunately that is not possible with -inteff- as far as I know.

Johannes 

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