st: RE: Interaction terms in logistic regression using dummy variables

["Chen, Xiao" <xiao@ats.ucla.edu>]

Hi Ashwin,

We have developed a suite of tools in Stata for visualizing main effects
and interactions for binary logit models. You are welcome to visit our
site for more information:

http://www.ats.ucla.edu/stat/stata/seminars/stata_vibl/default.htm



Xiao Chen
Statistical Consulting Group
UCLA Academic Technology Services
http://www.ats.ucla.edu/stat/



-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Ashwin
Ananthakrishnan
Sent: Wednesday, July 20, 2005 2:57 PM
To: statalist@hsphsun2.harvard.edu
Cc: ashwinna@yahoo.com
Subject: st: Interaction terms in logistic regression using dummy
variables

Hi,

I'm having some trouble interpreting the interaction
terms in logistic regression using stata.

My two variables of interest are gender (0-male,
1-female), and age categories (0- 65-69, 1-70-74,
2-75-79, 4-80 and above), and my outcome variable is
anyscreen.
When i type in the command,
xi: logistic anyscreen i.gender*i.income, I get the
following terms
-Igender_1, _Iagecat_1, _Iagecat_2, _Iagecat_3,
_IgenXage_~1,_IgenXage_~2, _IgenXage_~3.

What do teh odds ratios for each of these terms mean -
especially the interaction terms. And how do I test
the significance of these interaction terms.

Thanks,
Ashwin   

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