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Re: st: Interaction effect or running seperate models


From   "Clive Nicholas" <clivelists@googlemail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Interaction effect or running seperate models
Date   Fri, 28 Sep 2007 05:32:54 +0100

Quang Nguyen wrote:

> Thanks so much for your excellent answer, I highly appreciate it. I
> have a follow-up question. Suppose, we run seperate OLS and have one
> significant coefficience; however the interation term in the signle
> equation is not significant. Waht can we say about the result.

You shouldn't even have to ask this question! If you have been using
interaction terms in your models, then you already ought to know what
they are meant to tell you.

Say you have an OLS model of the response (Y) as a function of, say,
three covariates (X1, X2 and X3), where X3 is the interaction of X1
and X2. If X3 is significant, then the effect of X1 on Y varies by
values of X2. If it isn't, it doesn't.

That's all there is to it.

-- 
Clive Nicholas

[Please DO NOT mail me personally here, but at
<clivenicholas@hotmail.com>. Thanks!]

"Courage is going from failure to failure without losing enthusiasm."
-- Winston Churchill
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