Date:         Mon, 25 Jun 2007 22:22:19 -0700
Reply-To:     David L Cassell <davidlcassell@MSN.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         David L Cassell <davidlcassell@MSN.COM>
Subject:      Re: Collinearity interpretation
In-Reply-To:  <200706251122.l5PAk28v020110@malibu.cc.uga.edu>
Content-Type: text/plain; format=flowed

jonas.bilenas@CHASE.COM replied:
>
>I agree with Peter.

Me too.

>                     The SVD method used by the COLLIN option is more
>accepted than VIF.  VIF will not identify collinearities involving the
>intercept term.  More information is provided by COLLIN to identify which
>variables are implicated in the collinear relationship and the option
>provides more insight on which variables to remove if a collinearity
>exists.
>
>Some modellers run the diagnostic after the final model is built, but I
>like to run at the start to get a clean base of variables to examine.
>
>Do people include interaction temrs and polynomial terms in their
>collinearity diagnostics?

Well, they should.  But I assume that many do not.  In fact, many people
seem to go out of their way to build as many highly-correlated variables
as is humanly possible, then trust icky things like stepwise regression to
drag them out of the morass they just created.

David
--
David L. Cassell
mathematical statistician
Design Pathways
3115 NW Norwood Pl.
Corvallis OR 97330

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