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Re: st: How to svyset when strata are used in some groups and not others

 From Steve Samuels To statalist@hsphsun2.harvard.edu Subject Re: st: How to svyset when strata are used in some groups and not others Date Mon, 5 Jul 2010 07:42:14 -0400

```Before we try to answer your question, please now tell us:

1. the complete design, including subsequent stages of sampling
2.  the purposes of the analyses--descriptive?  estimating regression
coefficients?  testing hypotheses?

What -svyset- commands have you tried to issue so far?

Steve

On Mon, Jul 5, 2010 at 5:06 AM, Louise Linsell
<Louise.Linsell@npeu.ox.ac.uk> wrote:
> Thank you for suggestions. We have already tried defining 9 strata; 6 for the common type of hospital, for which we used stratified random sampling with 6 strata,  and 1 stratum each for the other 3 types of hospital, for which we took all units.
>
> However, in the model we had to specify a finite population correction (FPC=sqrt(1-n/N)) as we sampled 28 out of 87 units for the most common type of hospital.
>
> Because we sampled ALL the units from the other 3 types of hospital we had to set the FPC to zero since n=N (which is specified as 1 in Stata as it requires you to specify n/N). This means that there are no variance estimates when we summarise any outcomes in the 3 less common types of hospital, because it thinks we have sampled the whole population within these hospitals (when in fact we took a consecutive number of patients over a period of 3 months).
>
> LL
>
>>>> Stas Kolenikov <skolenik@gmail.com> 02/07/2010 20:36 >>>
> If Louise sampled other 3 types lumping them together, then Steve's
> recommendation is appropriate. If sampling was performed within each
> of those remaining types, then the strata variable will have 6 (strata
> in the most common type of hospitals) + 3 (other types of hospitals) =
> 9 levels.
>
> On Fri, Jul 2, 2010 at 11:18 AM, Steve Samuels <sjsamuels@gmail.com> wrote:
>> Louise-- create a stratum variable with 7 values: 1-6 for the
>> hospitals of the first type, and 7 for the other three types, and use
>> that in the strata() option of -svyset-
>>
>> Steve
>>
>> On Fri, Jul 2, 2010 at 12:00 PM, Louise Linsell
>> <Louise.Linsell@npeu.ox.ac.uk> wrote:
>>> I have a dataset with 4 different types of hospital, and would like to compare binary outcomes between them using logistic regression.  However for the first type  (the most common), hospitals were divided into 6 strata (based on size and SES) and a random sample was taken from each strata.  For the other 3 types of hospital we sampled all hospitals. My question is, how to use the svyset command when a different sampling strategy was used in one group?
>>>
>>> LL
>>>
>>>
>>>
>>>
>>> *
>>> *   For searches and help try:
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>>> *   http://www.ats.ucla.edu/stat/stata/
>>>
>>
>>
>>
>> --
>> Steven Samuels
>> sjsamuels@gmail.com
>> 18 Cantine's Island
>> Saugerties NY 12477
>> USA
>> Voice: 845-246-0774
>> Fax:    206-202-4783
>>
>> *
>> *   For searches and help try:
>> *   http://www.stata.com/help.cgi?search
>> *   http://www.stata.com/support/statalist/faq
>> *   http://www.ats.ucla.edu/stat/stata/
>>
>
>
>
> --
> Stas Kolenikov, also found at http://stas.kolenikov.name
> Small print: I use this email account for mailing lists only.
>
> *
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>
>
> *
> *   For searches and help try:
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> *   http://www.ats.ucla.edu/stat/stata/
>

--
Steven Samuels
sjsamuels@gmail.com
18 Cantine's Island
Saugerties NY 12477
USA
Voice: 845-246-0774
Fax:    206-202-4783

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/
```