Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: st: using -mixed- with clustered data that includes probability weights
From
Steve Samuels <[email protected]>
To
[email protected]
Subject
Re: st: using -mixed- with clustered data that includes probability weights
Date
Thu, 27 Feb 2014 21:48:36 -0500
To elaborate on Stas's post: if doctors were not sampled, then you can
define the doctor-level weight with pweight(1).
Steve
[email protected]
On Feb 27, 2014, at 8:21 PM, Stas Kolenikov <[email protected]> wrote:
Whether your results are biased really depends on your study design.
-mixed- knows nothing about your design (Stata 14 request: a command
to read the pdf file and extract the design information from the
narrative -- may I suggest -pdf2svyset- as a prospective name? I am
sure a lot of researchers would find this handy), and just warns you
in case you had sampling at several levels. If there were no sampling
at the doctor's level, then weighting only at the patient level that
you have is appropriate.
-- Stas Kolenikov, PhD, PStat (ASA, SSC)
-- Principal Survey Scientist, Abt SRBI
-- Opinions stated in this email are mine only, and do not reflect the
position of my employer
-- http://stas.kolenikov.name
On Thu, Feb 27, 2014 at 7:55 PM, Stephen Henry <[email protected]> wrote:
> Hi,
>
> I want to know whether I can used -mixed- in Stata 13.1 to analyze
> clustered data that include probability weights.
>
> My data were collected to study patients during clinic visits.
> Each patient is unique, and patients are clustered within doctors.
> In addition, patients were sampled based on an illness severity score.
> Patients with more severe symptoms were over-sampled.
> Patient sampling was done independent of which doctor was seeing the
> patient.
>
> I have been analyzing data using the -reg- command and cluster option as
> follows:
>
> reg v1 v2 v3 [pweight=weight], cluster(doctor_id)
>
> However, I'd like to use -mixed- instead to take advantage of the
> additional postestimation commands.
>
> Stata will run the following command:
>
> mixed v1 v2 v3 [pweight=weight] || doctor_id:
>
> but warns me that "Sampling weights were specified only at the first level
> in a multilevel model."
> Are my results with the -mixed- command potentially biased? If so, is
> there an easy way to fix this?
>
> Thanks in advance,
>
> Stephen Henry
> University of California Davis
> Sacramento, California
> *
> * For searches and help try:
> * http://www.stata.com/help.cgi?search
> * http://www.stata.com/support/faqs/resources/statalist-faq/
> * http://www.ats.ucla.edu/stat/stata/
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/faqs/resources/statalist-faq/
* http://www.ats.ucla.edu/stat/stata/
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/faqs/resources/statalist-faq/
* http://www.ats.ucla.edu/stat/stata/