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Re: st: Logistic regression interpretation


From   "Dr. Bill Westman" <webicky@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Logistic regression interpretation
Date   Tue, 21 Sep 2010 15:11:39 -0700

I apologize for the math error (7 times higher - not 6.)  - Also - Is
the command

listcoef, help percent

logistic (N=308): Percentage Change in Odds

  Odds of: no vs yes

----------------------------------------------------------------------
       abuse |      b         z     P>|z|      %      %StdX      SDofX
-------------+--------------------------------------------------------
     Risk |   1.56659    2.898   0.004    379.0     49.8     0.2580
       group |   0.74725    1.732   0.083    111.1     44.8     0.4952
----------------------------------------------------------------------

indicating that the odds of survival are 111% higher for Treatment
group?  and if so - is that 111% at both High/Low risk Levels?

On Tue, Sep 21, 2010 at 2:36 PM, Dr. Bill Westman <webicky@gmail.com> wrote:
> 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 7 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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