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Re: st: Rescaling odds ratios


From   "Tim Wade" <wadetj@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Rescaling odds ratios
Date   Thu, 22 May 2008 22:07:45 -0400

If you don't want to generate a new variable you can do this is by
using lincom after your estimation command.

e.g.,

. sysuse auto.dta

. logistic foreign price

Logit estimates                                   Number of obs   =         74
                                                  LR chi2(1)      =       0.17
                                                  Prob > chi2     =     0.6784
Log likelihood =  -44.94724                       Pseudo R2       =     0.0019

------------------------------------------------------------------------------
     foreign | Odds Ratio   Std. Err.      z    P>|z|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
       price |   1.000035   .0000844     0.42   0.676     .9998699    1.000201
------------------------------------------------------------------------------

. lincom 1000*price

 ( 1)  1000.0 price = 0.0

------------------------------------------------------------------------------
     foreign | Odds Ratio   Std. Err.      z    P>|z|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
         (1) |    1.03591   .0873912     0.42   0.676     .8780379    1.222168
------------------------------------------------------------------------------

hope this helps, Tim


On Thu, May 22, 2008 at 3:46 PM,  <BARTHRILEY@comcast.net> wrote:
> Dear Statalist
>
> I am performing a logistic regression using xtlogit. Some of my predictors
> are measured in days of treatment. Is there a way to recalculate the OR for
> a different unit of days, i.e., 30 days of treatment? Or would I have to
> transform the variable (e.g., dividing the per day variable by 30)?
>
> Thanks
>
> Barth
>
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