...
I agree with Clive's comment regarding the use of step-wise regression.
More to the point, however, why do you think that exponentiating the
coefficients from a linear regression will give you odds ratios?
______________________________________________
Kieran McCaul MPH PhD
WA Centre for Health & Ageing (M573)
University of Western Australia
Level 6, Ainslie House
48 Murray St
Perth 6000
Phone: (08) 9224-2701
Fax: (08) 9224 8009
email: [email protected]
http://myprofile.cos.com/mccaul
http://www.researcherid.com/rid/B-8751-2008
______________________________________________
If you live to be one hundred, you've got it made.
Very few people die past that age - George Burns
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Tina
Hernandez-Boussard
Sent: Friday, 4 September 2009 1:54 AM
To: [email protected]
Subject: st: regression using eform
Hi,
I have a question regarding a regression model that I am running. I
am looking at predictors for a variable slope, which is growth of a
tumor per day. I have ran this model and using
sw, pr(.2):regress slope smoker exercise bmi , eform(odds)
I have reran the model, only multiplying the slope by 365.25 to get
the growth per year. I did not think that this would change
anything, yet it changes the odds ratios. I still get the same
prob>f, r-squared, and adjusted r-squared. However, model and
residual ss, df, and ms are different.
Can someone please explain why my odds ratios are changing, yet the t
and P>|t| are not?
First model:
------------------------------------------------------------------------
---
slope | odds Std. Err. t P>|t| [95% Conf.
Interval]
-------------
+----------------------------------------------------------------
exercise | 1.000341 .0001396 2.45 0.017
1.000062 1.00062
bmi | .9999843 9.47e-06 -1.66 0.102 .
9999653 1.000003
smoker | 1.000748 .0003167 2.36 0.021
1.000116 1.001382
Model with slope*365.25:
------------------------------------------------------------------------
------
growth | odds Std. Err. t P>|t| [95% Conf.
Interval]
-------------
+----------------------------------------------------------------
exercise | 1.132765 .0577325 2.45 0.017
1.023043 1.254254
bmi | .9942751 .0034406 -1.66 0.102 .
9874212 1.001177
smoker | 1.314259 .1519301 2.36 0.021
1.043092 1.655921
Thanks,
Tina
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