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# Re: st: Number of Obs with svy , suppop()

 From Tim Scharks To statalist@hsphsun2.harvard.edu Subject Re: st: Number of Obs with svy , suppop() Date Thu, 18 Mar 2010 21:14:28 -0700

```That sounds reasonable, Phil, but why are the WOMEN with (missing) for
race added to the sample when men==1 was specified?

Thanks, Tim

takes on values other than 0 and 1
subpop() != 0 indicates subpopulation
(running tabulate on estimation sample)

Number of strata   =         1                  Number of obs      =      4000
Number of PSUs     =      4000                  Population size    = 7880496.9
Subpop. no. of obs =      4000
Subpop. size       = 7880496.9
Design df          =      3999

------------------------
1=white,  |
2=black,  |
3=other   |        count
----------+-------------
White | 6,930,316.91
Black |   754,879.69
Other |   195,300.31
|
Total | 7,880,496.91
------------------------
Key:  count     =  weighted counts

.
end of do-file

On Thu, Mar 18, 2010 at 5:04 PM, Phil Schumm <pschumm@uchicago.edu> wrote:
> On Mar 18, 2010, at 6:20 PM, Michael Mitchell wrote:
>>
>> Here is the tabulation of race and sex by race.
>
> <snip>
>
>> . tab sex race, missing
>>
>>   1=male, |          1=white, 2=black, 3=other
>>  2=female |     White      Black      Other          . |     Total
>> -----------+--------------------------------------------+----------
>>      male |     1,676        193         35         34 |     1,938
>>    female |     1,824        238         34         37 |     2,133
>> -----------+--------------------------------------------+----------
>>     Total |     3,500        431         69         71 |     4,071
>
> <snip>
>
>> But now I want to analyze just the sub-population of males (sex==1) and it
>> shows that the number of obs is now 4037 (see below). How can the number of
>> observations increase when adding a -subpop()- option?  There are suddenly
>> 37 extra observations. Note this corresponds to the number of females with a
>> missing race.
>>
>> . svy , subpop(if sex==1): tab race, count format(%13.2fc)
>> (running tabulate on estimation sample)
>>
>> Number of strata   =         1                  Number of obs      =
>>  4037
>> Number of PSUs     =      4037                  Population size    =
>> 7932333.9
>>                                                Subpop. no. of obs =
>>  1904
>>                                                Subpop. size       =
>> 3780355.3
>>                                                Design df          =
>>  4036
>
>
> This is as it should be, since information about race is not required on
> those observations outside of the subpopulation.  Remember, observations
> outside the subpopulation are relevant only insofar as they reflect the
> variability in the proportion(s) of sampled PSUs with at least one
> observation in the subpopulation.
>
> In fact, at one point Stata did not behave properly in this regard; this was
> fixed in an update to Stata 10 on 02apr2008 (see -help whatsnew10- and
> search for "02apr2008").
>
>
> -- Phil
>
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```