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From |
Maarten Buis <maartenlbuis@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Intepretation of interaction terms |

Date |
Tue, 24 May 2011 09:41:15 +0200 |

On Tue, May 24, 2011 at 9:15 AM, lreine ycenna <lreine.ycenna@gmail.com> wrote: > In fact, > another similar question: > > y = a + b + a x b > > I want to test this equation for group1 (dummy G1 ==1), while a , b, y > are numeric. > > In Stata, it would be: > > regress y a b axb G1 axG1 bxG1 axbxG1 > > we must include G1 individually in the equation. That is not necessarily true, it just depends on what you want. > Also, we need to add up the coef of G1 to get the true effect for this group. That is also not necessarily true. > My question is, since G1 is a dummy, how should we interprete G1? i.e. > what does the coefficient for G1 mean to Y (GDP)? That depends on how you set up your model and how you choose to interpret your results. Typically with interaction effects there are multiple interpretations possible. You seem to be looking for a "cook book recipe" for doing interaction effects, and no such thing exists. Typically there multiple ways of correctly estimating the same model (and many more ways to do it incorrectly). The only way of doing this right is to understand the logic and derive the model yourself. Deriving once own model sounds hard, but it is not. The only hard part is not making mistakes (it is easy to forget a minus sign or misplace a bracket), but that is just a matter of concentration. Even though I say it is easy, it is probably best learned by doing this a couple of times with someone who can give you face to face feed back while you are doing this. I suggest you find someone in your institution who can spare you an hour or so, and lets you go through successively more difficult examples till you get to your actual model of interest. Hope this helps, Maarten -------------------------- Maarten L. Buis Institut fuer Soziologie Universitaet Tuebingen Wilhelmstrasse 36 72074 Tuebingen Germany http://www.maartenbuis.nl -------------------------- * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: Intepretation of interaction terms***From:*lreine ycenna <lreine.ycenna@gmail.com>

**References**:**st: Intepretation of interaction terms***From:*lreine ycenna <lreine.ycenna@gmail.com>

**Re: st: Intepretation of interaction terms***From:*Maarten Buis <maartenlbuis@gmail.com>

**Re: st: Intepretation of interaction terms***From:*lreine ycenna <lreine.ycenna@gmail.com>

**Re: st: Intepretation of interaction terms***From:*Maarten Buis <maartenlbuis@gmail.com>

**Re: st: Intepretation of interaction terms***From:*lreine ycenna <lreine.ycenna@gmail.com>

**Re: st: Intepretation of interaction terms***From:*lreine ycenna <lreine.ycenna@gmail.com>

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