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


From   Tim Scharks <tim.scharks@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Number of Obs with svy , suppop()
Date   Thu, 18 Mar 2010 21:33:46 -0700

Sorry all, I understand Phil's point--they are added to the total
population, not the subpopulation.

The bit I pasted below was unintentional, I thought that it might have
something to do with the missing data but no...then didn't delete it.
Sorry!

Cheers, Tim

On Thu, Mar 18, 2010 at 9:14 PM, Tim Scharks <tim.scharks@gmail.com> wrote:
> 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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>>
>

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