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st: RE: relative risk


From   "Steichen, Thomas" <STEICHT@rjrt.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: relative risk
Date   Wed, 16 Jul 2003 17:08:04 -0400

I don't see what you are referring to, Wendell.  The p-values 
(labeled "P>|Z|") appear to be changing to me.  What did not 
change is Po, which is defined as "the incidence of the outcome 
(dependent variable = 1) in the unexposed group."  This should not
change based on # of predictors in the model.

Tom

> -----Original Message-----
> From: Wendell Joice [mailto:wjoice@erols.com] 
> Sent: Wednesday, July 16, 2003 4:55 PM
> To: statalist@hsphsun2.harvard.edu
> Subject: st: relative risk 
> 
> 
> I am using Stata 7 and the -relrisk- (ado) command in conjunction
> ith  -logistic-. I note that, for my data, the p value (for a given
> covariate) never changes, regardless of how many or which 
> variables I add to
> the model. For example, in the data below, I am using a 
> dependent variable
> (psyment) with a covariate (racewbh). The relative risk ratios for
> _Iracewbh_2  &  _Iracewbh_3 change as I add other covariates 
> to the model;
> but the p value for these two variables never changes  (see 
> small and large
> models below).
> 
> Is this the way it should be or am I in error with my data? 
> My usage of
> the -relrisk- command?
> Is there a simple way to check (verify) the output of the 
> -relrisk- command?
> 
> Thanks,
> Wendell Joice
> 
> 
> 
> SMALL MODEL
> 
> xi: logistic psyment i.racewbh if csample==1
>       i.racewbh         _Iracewbh_1-3       (naturally coded; 
> _Iracewbh_1
> omitted)
> 
>       Logit estimates                                   
> Number of obs   =
> 19295
>                                                         LR 
> chi2(2)      =
> 68.54
>                                                         Prob 
> > chi2     =
> 0.0000
>       Log likelihood = -12961.957                       
> Pseudo R2       =
> 0.0026
> 
>       
> ----------------------------------------------------------------------
> --------
>            psyment | Odds Ratio   Std. Err.      z    P>|z|   
>   [95% Conf.
> Interval]
>       
> -------------+--------------------------------------------------------
> --------
>        _Iracewbh_2 |   .6429203   .0385832    -7.36   0.000   
>   .5715766
> .723169
>        _Iracewbh_3 |   .7907062   .0466184    -3.98   0.000   
>   .7044174
> .8875651
>       
> ----------------------------------------------------------------------
> --------
> 
>     relrisk
>                                       Po             Rel Risk 
>       Lower
> Limit    Upper Limit
>       RR _Iracewbh_2:    0.066          0.658          0.588  
>         0.737
>       RR _Iracewbh_3:    0.065          0.802          0.718  
>         0.894
> 
> 
> LARGER MODEL BELOW
> 
> xi: logistic psyment i.racewbh i.physpecy i.psydin2 
> i.phytimec i.chrcadg
> i.di
>       > agsrvc  i.acutcadg i.newinsur i.likreccdg i.psydrnumx 
> i.agecatc
> i.GEOGREGN i.
>       > yearmhp if csample==1
> 
> (output abbreviated)
> 
>       Logit estimates                                   
> Number of obs   =
> 18110
>                                                         LR 
> chi2(30)     =
> 11484.07
>                                                         Prob 
> > chi2     =
> 0.0000
>       Log likelihood = -6465.4055                       
> Pseudo R2       =
> 0.4704
> 
>       
> ----------------------------------------------------------------------
> --------
>            psyment | Odds Ratio   Std. Err.      z    P>|z|   
>   [95% Conf.
> Interval]
>       
> -------------+--------------------------------------------------------
> --------
>        _Iracewbh_2 |   .8734043   .0805943    -1.47   0.142   
>   .7289031
> 1.046552
>        _Iracewbh_3 |   .9309302   .0823622    -0.81   0.419   
>   .7827242
> 1.107199
>       _Iphyspecy_2 |   .5840736   .0408614    -7.69   0.000   
>   .5092348
> .6699109
>       _Iphyspecy_3 |   10.01045   .8514816    27.08   0.000   
>   8.473265
> 11.82649
>       ..........................................Output
> abbreviated......................
> 
>        _Iyearmhp_6 |   .4989542   .0376058    -9.22   0.000   
>   .4304337
> .5783824
>       
> ----------------------------------------------------------------------
> --------
> 
>     relrisk
>                                       Po             Rel Risk 
>       Lower
> Limit    Upper Limit
>       RR _Iracewbh_2:    0.066          0.881          0.742  
>         1.043
>       RR _Iracewbh_3:    0.065          0.935          0.794  
>         1.100
>       RR _Iphyspecy_2:   0.168          0.628          0.555  
>         0.709
>       RR _Iphyspecy_3:   0.016          8.764          7.579  
>         10.100
>       ............................................Output
> abbreviated...............................
>       RR _Iyearmhp_5:    0.059          0.773          0.667  
>         0.896
>       RR _Iyearmhp_6:    0.061          0.515          0.446  
>         0.594
> 
> 
> 
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