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st: RE: Logistic regression interpretation


From   "Kieran McCaul" <Kieran.McCaul@uwa.edu.au>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Logistic regression interpretation
Date   Wed, 22 Sep 2010 09:56:14 +0800

...

low risk, control group: OR=1.00 (ref)
high risk, control group: OR=2.11
low risk, treatment group: OR=4.79
high risk, treatment group: OR=2.11*4.79=10.11

This assumes no multiplicative interaction between Risk and group.





-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Dr. Bill
Westman
Sent: Wednesday, 22 September 2010 5:36 AM
To: statalist@hsphsun2.harvard.edu
Subject: st: Logistic regression interpretation

Dear Listers: I have more of a stats question than a stata question,
but here goes:

A simple logistic regression was run - outcome - Survived/Non Survived
(1/0), with Group(Treatmeant/Control -- 1/0) & Risk(High/Low -- 1/0)

The results
------------------------------------------------------------------------
------
       Survived | Odds Ratio   Std. Err.      z    P>|z|     [95%
Conf. Interval]
-------------+----------------------------------------------------------
------
    Risk |   4.790295   2.589136     2.90   0.004     1.660699
13.81763
   group |   2.111181   .9107981     1.73   0.083     .9063649
4.917538
------------------------------------------------------------------------
------

Assuming the .10 level of significance was acceptable (for discussion
purposes)

Can I assume that odds of treatment survival were 2.1  times higher in
the treatment Group for LOW risk patients?
And for High Risk patients in the treatment group is the adds 4. 8 +
2.1 (or 6 times higher)?

Other than test for interactions, can I run a graphs of these two
groups?

Can I estimate the "average" effect of Treatment across both high and
low risk patients?  If so, how?

What other tests might I wish to do in Stata?

Thanks

Bill
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