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Re: st: Re: Why main effects are significant but interction term is not signficant
From
Richard Williams <[email protected]>
To
[email protected]
Subject
Re: st: Re: Why main effects are significant but interction term is not signficant
Date
Tue, 08 Mar 2011 10:33:16 -0500
At 07:22 AM 3/8/2011, Mike wrote:
y= beta+beta1*x1+beta2*x2+beta3*x1*x2+epsilon
You can think of y as income, x1 is gender (1 for male) and x2 is the
educational level.
The OLS gives a significant results for beta1 and beta2 but not
beta3. In the context of the example, male and higher education help
having higher income. But the interaction of male and higher education
doesn't have any significant effect on income. Can you provide some
insights?
I'm not sure why there is a question -- there is nothing that says
the interaction has to be significant. Perhaps you are thinking this
means that education does not affect males, but if so that is the
wrong interpretation. As has already been pointed out, if there is no
interaction then the effect of education is the same for both men and women.
As luck would have it, I just talked about interactions in class
yesterday, so if you want a basic explanation you can see
http://www.nd.edu/~rwilliam/xsoc63993/l51.pdf
http://www.nd.edu/~rwilliam/xsoc63993/l53.pdf
-------------------------------------------
Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
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EMAIL: [email protected]
WWW: http://www.nd.edu/~rwilliam
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