Logistic regression shows odds ratio, then what margins show? the risk? See

[Tom Hsiung]

After logistic regression, odds ratio were reported. I used the syntax of 'margins' to get other result. It seems that these results from margins were risk rather than odds. If margins resulted in risk rates, how to change the output of logistic regression from odds ratio (by default it's odds ratio) to risk ratio? Much appreciated!

Tom

. logistic firsttherapeuticinrreached i.nonaaornonanona i.ageforttest i.af i.ttesttargetinr

Logistic regression                             Number of obs     =        187
                                                LR chi2(4)        =      25.32
                                                Prob > chi2       =     0.0000
Log likelihood = -84.409294                     Pseudo R2         =     0.1304

--------------------------------------------------------------------------------------------
firsttherapeuticinrreached | Odds Ratio   Std. Err.      z    P>|z|     [95% Conf. Interval]
---------------------------+----------------------------------------------------------------
         1.nonaaornonanona |   .1526829    .073589    -3.90   0.000     .0593656    .3926867
             1.ageforttest |   2.916752   1.356175     2.30   0.021     1.172531    7.255625
                      1.af |   .3494673    .161598    -2.27   0.023     .1411888    .8649931
          1.ttesttargetinr |   2.409212    1.35103     1.57   0.117     .8026778    7.231175
                     _cons |   4.008227   1.200546     4.64   0.000     2.228436    7.209492
--------------------------------------------------------------------------------------------

. margins i.nonaaornonanona

Predictive margins                              Number of obs     =        187
Model VCE    : OIM

Expression   : Pr(firsttherapeuticinrreached), predict()

---------------------------------------------------------------------------------
                |            Delta-method
                |     Margin   Std. Err.      z    P>|z|     [95% Conf. Interval]
----------------+----------------------------------------------------------------
nonaaornonanona |
             0  |   .8367911   .0286637    29.19   0.000     .7806114    .8929709
             1  |   .4675317   .0984477     4.75   0.000     .2745778    .6604856
---------------------------------------------------------------------------------

. margins r.nonaaornonanona

Contrasts of predictive margins
Model VCE    : OIM

Expression   : Pr(firsttherapeuticinrreached), predict()

---------------------------------------------------
                |         df        chi2     P>chi2
----------------+----------------------------------
nonaaornonanona |          1       12.88     0.0003
---------------------------------------------------

-----------------------------------------------------------------
                |            Delta-method
                |   Contrast   Std. Err.     [95% Conf. Interval]
----------------+------------------------------------------------
nonaaornonanona |
      (1 vs 0)  |  -.3692594   .1028906     -.5709214   -.1675975
-----------------------------------------------------------------

[Carlo Lazzaro]

Tom:
the reported metric is the predicted probability of a positive outcome (see -help margins-; -help logistic postestimation-).

[Tom Hsiung]

Tom:
the reported metric is the predicted probability of a positive outcome (see -help margins-; -help logistic postestimation-).

So the reported metric of margins is the risk rates of two groups by i.variable, and the output of margins r.variable is the absolute risk difference between two groups. However, I want the output of -logistic indep dep1, dep2, ... depk- to show the risk ratio rather than odds ratio. Possible?

Tom

[Marcos Almeida]

This issue was already approached here.

[Tom Hsiung]

This issue was already approached here.

Thanks for your explanation. I use 'logit' (logistic would output odds ratio instead of coef.) and it results in a same result, with the exception that coef. were reported. Just don't know how to output risk ratio.