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st: AW: Interacting dummies and multicollinearity issue


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: AW: Interacting dummies and multicollinearity issue
Date   Wed, 23 Jun 2010 13:53:50 +0200

<> 

You should check

*************
help fvvarlist
*************

Redundancies are tossed out automatically during estimation.


HTH
Martin


-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Özlen D. Luznar
Gesendet: Mittwoch, 23. Juni 2010 13:51
An: statalist@hsphsun2.harvard.edu
Betreff: st: Interacting dummies and multicollinearity issue

Hi everyone,

I am using a recursive biprobit model.  I have 2 separate categorical
variables.

variable d - has 3 values - dummied out to d1 d2 d3
variable e has 4 values dummied out to e1 e2 e3 e4

In addition to include d1 d2 e1 e2 e3 in my model I want to include
interaction terms between d dummies and e dummies:

12 possible variables interaction between d dummies and e dummies.  Among
these 12 I know that at least 3 dummies have only one value and that is 0,
in other words d2*e2 == 0 for everyone, d3*e1 == 0 for everyone and
d2*e1==0 for everyone.

I am confused as to which of these 12 I can/should include in the model so
as to avoide multicollinearity.

This may be a basic question but I appreciate any help you may give me.

Thanks!

Ozlen



-- 
Özlen D. Luznar

PhD Candidate - Public Policy
Graduate Research Assistant
University of Maryland Baltimore County (UMBC)
1000 Hilltop Circle
Baltimore, MD 21250

443-846-5010




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