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st: RE: predictive margins not estimable in svy


From   susan@hailpern.com
To   statalist@hsphsun2.harvard.edu
Subject   st: RE: predictive margins not estimable in svy
Date   Fri, 07 Aug 2009 17:55:28 -0700

Thank you to all-
My error in posting....I am using Stata 11.

I have also tried what Michael Lichter suggested with similar results
using this command:

margins i.x , subpop(if subpopnodm==1) vce(unconditional)

The small section on margins in the svy estimation does not provide much
additional help.
Any other thoughts would be appreciated.

Sue

> 
> 
> Hello,
> 
> I am having problems using the Stata 10 "margins" command with survey
> data.  
> 
> I have a created a subpop of ~2500 observations (total 5000+) and would
> like to obtain the age- sex- race adjusted prevalence of my dichotomous
> outcome by cystatin-c quartile. Data is svyset; svy logistic model
> including age, sex and race and cystatin-c was run, followed by the
> marginals command.  
> 
> The output says (not estimable). (below)
> 
> Can anyone help?  I do get estimations if I take it out of survey mode,
> Thanks,
> Sue
> 
> . svy, subpop(subpopnodm): logistic pad i.x age56 sex01 race2
> (running logistic on estimation sample)
> 
> Survey: Logistic regression
> 
> Number of strata   =        28                 Number of obs      =     
>  5684
> Number of PSUs     =        57                 Population size    = 
> 230532837
>                                                Subpop. no. of obs =     
>  2472
>                                                Subpop. size       =
> 90812359.8
>                                                Design df          =     
>    29
>                                                F(   6,     24)    =     
> 28.73
>                                                Prob > F           =    
> 0.0000
> 
> ------------------------------------------------------------------------------
>              |             Linearized
>          pad | Odds Ratio   Std. Err.      t    P>|t|     [95% Conf.
> Interval]
> -------------+----------------------------------------------------------------
>            x |
>           2  |   1.521746   .5364044     1.19   0.243     .7400256    
> 3.12923
>           3  |   4.057542   2.135947     2.66   0.013     1.382564   
> 11.90805
>           4  |   9.510348   3.931692     5.45   0.000     4.083106   
> 22.15145
>              |
>        age56 |   4.655526   2.164545     3.31   0.003     1.798843   
> 12.04881
>        sex01 |    1.14324    .236113     0.65   0.522      .749361   
> 1.744149
>        race2 |   2.314983   .5035135     3.86   0.001     1.483732   
> 3.611936
> ------------------------------------------------------------------------------
> 
> . margins i.x , subpop(if subpopnodm==1)
> 
> Predictive margins                                Number of obs   =     
>  3009
>                                                   Subpop. no. obs =     
>  2472
> Model VCE    : Linearized
> 
> Expression   : Pr(pad), predict()
> 
> ------------------------------------------------------------------------------
>              |            Delta-method
>              |     Margin   Std. Err.      z    P>|z|     [95% Conf.
> Interval]
> -------------+----------------------------------------------------------------
>            x |
>           1  |  (not estimable)
>           2  |  (not estimable)
>           3  |  (not estimable)
>           4  |  (not estimable)
> ------------------------------------------------------------------------------


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