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st: somersd: clustering with wstrata ?


From   "alan.h.feiveson@nasa.gov" <alan.h.feiveson@nasa.gov>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: somersd: clustering with wstrata ?
Date   Fri, 9 May 2008 10:11:40 -0700

Hi - I wish to compare two variables within repeated observations on
subjects using -somersd-.  If I use the "wstrata" option, would the
standard error also be adjusted to take care of the non-independent
observations pertaining to the same subject? Apparently I can't use
"cluster" and "wstrata" on the same variable. I don't think I want to
use "cluster" alone if I want the comparisons to be within each subject.


Al Feiveson

. somersd z6a age,wstrata(id)
Symmetric 95% CI
------------------------------------------------------------------------
------
             |              Jackknife
         z6a |      Coef.   Std. Err.      z    P>|z|     [95% Conf.
Interval]
-------------+----------------------------------------------------------
------
         age |   .3608484   .0250542    14.40   0.000      .311743
.4099537

. somersd z6a age,wstrata(id) cluster(id)
Symmetric 95% CI
                                   (Std. Err. adjusted for 403 clusters
in id)
------------------------------------------------------------------------
------
             |              Jackknife
         z6a |      Coef.   Std. Err.      z    P>|z|     [95% Conf.
Interval]
-------------+----------------------------------------------------------
------
         age |  (dropped)
------------------------------------------------------------------------
------

. somersd z6a age,cluster(id)
Symmetric 95% CI
                                   (Std. Err. adjusted for 403 clusters
in id)
------------------------------------------------------------------------
------
             |              Jackknife
         z6a |      Coef.   Std. Err.      z    P>|z|     [95% Conf.
Interval]
-------------+----------------------------------------------------------
------
         age |   .4528894   .0239833    18.88   0.000     .4058829
.4998958
------------------------------------------------------------------------
------






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