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Re: st: OR results of mhodds vs. logistic


From   Suzy <scott_788@wowway.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: OR results of mhodds vs. logistic
Date   Fri, 26 May 2006 09:29:06 -0400

Sorry, I sent the incorrect output in the previous e-mail - the question and correct output are below:

Dear Statalisters:
I think this might be more of a statistical question rather than a Stata question. I would like to know why the odds ratio estimate, as an approximation to the odds ratio
for a one unit increase in x1 (x1 is continuous) for the mhodds command is so different than the logistic output from the command below. FYI, x2 is continuous as well. Both x1 and x2 are linear in the logit.
Suzy


OR results for x1 controlling for x2 are different for the mhodds command and the logistic command below:


mhodds Y x1 x2(x2 is controlled) by(x3)

-------------------------------------------------------------------------------
Y | Odds Ratio chi2(1) P>chi2 [95% Conf. Interval]
----------+--------------------------------------------------------------------
1 | 1.154021 21.50 0.0000 1.08622 1.22606
2 | 1.095894 5.87 0.0154 1.01764 1.18017
3 | 1.073977 3.63 0.0566 0.99799 1.15574
4 | 1.308015 5.38 0.0203 1.04258 1.64103
5 | 1.004919 0.00 0.9552 0.84669 1.19271
-------------------------------------------------------------------------------


by x3, sort : logistic dmcat x1 x2

> x3 = 1


------------------------------------------------------------------------------
Y | Odds Ratio Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
x1 | 1.18209 .039921 4.95 0.000 1.10638 1.262982
x2 | 1.051794 .0060071 8.84 0.000 1.040086 1.063634
------------------------------------------------------------------------------

------------------------------------------------------------------------------
-> x3 = 2

------------------------------------------------------------------------------
Y | Odds Ratio Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
x1 | 1.119092 .0440137 2.86 0.004 1.036067 1.208769
x2 | 1.063327 .0077098 8.47 0.000 1.048323 1.078546
------------------------------------------------------------------------------

------------------------------------------------------------------------------
-> x3 = 3


------------------------------------------------------------------------------
Y | Odds Ratio Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
x1 | 1.110412 .0408657 2.85 0.004 1.033137 1.193467
x2 | 1.068197 .0067078 10.51 0.000 1.055131 1.081426
------------------------------------------------------------------------------

------------------------------------------------------------------------------
-> x3 = 4

------------------------------------------------------------------------------
Y | Odds Ratio Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
x1 | 1.211418 .1138217 2.04 0.041 1.007668 1.456367
x2 | 1.05441 .0171186 3.26 0.001 1.021387 1.088502
------------------------------------------------------------------------------

------------------------------------------------------------------------------
-> x3 = 5

------------------------------------------------------------------------------
Y | Odds Ratio Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
x1 | 1.007958 .0746672 0.11 0.915 .8717407 1.16546
x2 | 1.045343 .0116738 3.97 0.000 1.022711 1.068475
------------------------------------------------------------------------------





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