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Re: st: predictive margins not estimable in svy


From   "Michael I. Lichter" <MLichter@Buffalo.EDU>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: predictive margins not estimable in svy
Date   Fri, 07 Aug 2009 20:25:25 -0400

Susan,

Where did you get this -margins- command? It's not part of Stata 10, and -findit- doesn't show anything.

-ml

susan@hailpern.com wrote:
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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--
Michael I. Lichter, Ph.D. <mlichter@buffalo.edu>
Research Assistant Professor & NRSA Fellow
UB Department of Family Medicine / Primary Care Research Institute
UB Clinical Center, 462 Grider Street, Buffalo, NY 14215
Office: CC 126 / Phone: 716-898-4751 / FAX: 716-898-3536

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