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Re: st: Svy mean using subpop and incorrect number of observations


From   jpitblado@stata.com (Jeff Pitblado, StataCorp LP)
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Svy mean using subpop and incorrect number of observations
Date   Wed, 23 Jul 2008 13:17:23 -0500

Heather Ridolfo <evd7@CDC.GOV> is using -svy: mean- with options -subpop()-
and -over()- and noticed that it is reporting a smaller estimation sample than
the number of observations in her dataset:

> I recently posted a question regarding losing observations and PSUs when
> using svy regress and the subpop command. Jeff Pitblado recommended I
> update the version of stata I was using to correct this problem. 
> 
> This did in fact fix the problem. However, I am still having a problem
> when I run svy, mean.
> 
> svyset psuscid [pweight = gswgt1], strata(region)
> svy, subpop(bhgsp): mean efficacy esteem child_sex age meduc new_inc2
> dm_support dm_college m_indep MDCOLLEG md_spprt MDACHIEV, over(racebh)
> 
> 
> Survey: Mean estimation
> 
> Number of strata =       4         Number of obs    =     4657
> Number of PSUs   =     121         Population size  =  3921354
>                                    Subpop. no. obs  =     2126
>                                    Subpop. size     =  1736680
>                                    Design df        =      117
> 
> If STATA is dropping observations from my original dataset due to
> incomplete data, is the survey design information from these
> observations retained in the calculation of the standard errors? Is
> there any way to fix this or another way to get means while using the
> survey commands and subpop?

We have verified that -svy: mean- is incorrectly dropping out-of-subpop
observations that contain missing values in the variables of the varlist.  The
only other affected commands are -svy: proportion-, -svy: ratio-, and
-svy: total-.  We hope to have this fixed in the next Stata update (within the
next few weeks).

--Jeff
jpitblado@stata.com
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