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Re: st: interaction without linear terms

From   Mirko <>
Subject   Re: st: interaction without linear terms
Date   Wed, 23 May 2007 14:39:21 +0100

I really invite you to have a look at this web page by Matt Golder
full of hints about multiplicative interaction terms, correct standard
errors and Stata codes, which is a companion of:

Thomas Brambor, William Roberts Clark, Matt Golder
"Understanding Interaction Models: Improving Empirical Analyses"
(Political Analysis 14: 63-82),

Regarding your point and in brief, they say:

"We recommend that scholars include all constitutive terms in their
interaction model specifications".

Hope this helps

On 5/23/07, Richard J Stoll <> wrote:
On Wed, 23 May 2007, Wanli Zhao wrote:

> I have a basic(?) econometric question on regressions with interactions. My
> search on this did not product much. Do I have to include the linear terms
> in the regression when I also have interactions (include x & y when I have
> x*y)?  What does it mean when I drop x, or y or BOTH (always keep x*y)? Any
> help is highly appreciated (occasions where different model is suitable),
> especially what I should get to read!


The "classic" article in political science is:
Friedrich, Robert. 1982. "In Defense of Multiplicative Terms in Multiple
Regression Equations." American Journal of Political Science 26: 797-833.

Richard J. Stoll * Professor of Political Science * Rice University
Dept. Political Science MS 24 * P.O. Box 1892 * Houston TX 77251-1892
E-mail: * Tel: 713-348-3362 * FAX: 713-348-5273

*   For searches and help try:

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