Re: st: using several years of survey data

[roland andersson <rolandersson@gmail.com>]

Rebecca

I have considered using the NIS data. I wonder if NIS can be used to
calculate indicence rates, ie is it at all possible to relate the data
to a defined population? For any geographic area or the nation?

Regards
> 2011/3/2 Rebecca Pope <rebecca.a.pope@gmail.com>
>>
>> Maria,
>> If you haven't already, you should consult the following documents
>> from HCUP (for those not familiar, HCUP publishes the NIS):
>>
>> - Calculating Nationwide Inpatient Sample Variances
>> http://www.hcup-us.ahrq.gov/reports/methods/CalculatingNISVariances200106092005.pdf
>>
>> - Using the HCUP Nationwide Inpatient Sample to Estimate Trends
>> http://www.hcup-us.ahrq.gov/reports/methods/2006_05_NISTrendsReport_1988-2004.pdf
>>
>> Combined, I think they'll answer any set-up questions you have. I
>> especially recommend the Trends document because the sampling frame
>> for the NIS has changed over time, as have their sample selection
>> methods (including strata definitions). They have guides for coping
>> with this in your research. There is also sample Stata code (in the
>> Variances document), though depending on which version of Stata you
>> are using, you will probably need to change the syntax. They use
>> version 8.
>>
>> If you have already read these documents & weren't able to have your
>> questions sufficiently answered, I endorse Steve's recommendation to
>> contact HCUP. The HCUP Technical Assistance contact information is all
>> online & in my experience they are very responsive.
>>
>> Regards,
>> Rebecca
>>
>>
>>
>>
>> On Wed, Mar 2, 2011 at 1:02 PM, Steven Samuels <sjsamuels@gmail.com> wrote:
>> >
>> > Maria, ordinarily I would say that your set up is correct.  However, sometimes in this kind of study (I'm not familiar with yours), the population is randomly divided into five groups of about equal size; then one group a year is surveyed. In 10 years, each group would appear twice. In this case, I don't know if the standard sampling formulas apply. I suggest that you contact the study statisticians for some guidance.
>> >
>> > Steve
>> > sjsamuels@gmail.com
>> >
>> >
>> > On Mar 1, 2011, at 4:22 PM, Maria E. Montez Rath wrote:
>> >
>> > Hello,
>> >
>> > I'm using 10 years of the National Inpatient Sample (NIS) and have a
>> > question on how to define the strata.
>> >
>> > The NIS is a stratified, single-stage cluster sample of hospitals.
>> > Every year, about 20% of US community hospitals are sampled. Sixty
>> > strata are defined depending on things like geographical region and
>> > teaching status, and from each a random sample of hospitals is taken.
>> > For each hospital all discharges are then selected.
>> >
>> > The data provided includes the strata and weights. I set the data by
>> >
>> > svyset hospid [pweight=discwt], strata (nis_stratum)
>> >
>> > When using several years, shouldn't I create a new strata variable
>> > that incorporates the year so that the strata is different per year?
>> >
>> > gen str yearstratum=string(year,"%04.0f") + string( nis_stratum,"%04.0f")
>> >
>> > svyset hospid [pweight=discwt], strata (yearstratum)
>> >
>> > I think this is necessary in order to obtain the correct standard errors.
>> >
>> > Can anyone correct me if I'm wrong or confirm that what I'm doing is right?
>> >
>> > Thank you,
>> >
>> > Maria
>> >
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>

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