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st: regression using eform


From   Tina Hernandez-Boussard <boussard@stanford.edu>
To   statalist@hsphsun2.harvard.edu
Subject   st: regression using eform
Date   Thu, 3 Sep 2009 10:53:50 -0700

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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