Bookmark and Share

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: combining multiple surveys - adjustment of weights


From   Steven Samuels <sjsamuels@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: combining multiple surveys - adjustment of weights
Date   Fri, 28 Jan 2011 10:52:57 -0500

I should clarify point 1. I meant, there is no statistical problem if all primary sampling units are defined in the same way. Example where this was the case: In some of our surveys of businesses, some were listed at each location where they operated; others had one listing that covered all locations. If we drew the sample only from the original list, there was a problem whether or not our intended sampling units were locations or the parent businesses.

Steve

On Jan 28, 2011, at 9:04 AM, Steven Samuels wrote:


On Jan 27, 2011, at 11:45 PM, Dana Shills wrote:


> I am trying to combine multiple country survey datasets (10 surveys) to > estimate ols regressions of firm performance across the 10 countries. 8 of > the surveys are stratified random samples of firms in the 8 countries (so > the strata identifier in each dataset goes from 1 to some number N, that > varies) and 2 others are simple random samples. The survey questionnaire
> is the same across countries.

> 1> Statistically are there any issues with combining multiple surveys when
> the sampling methods are different?

Not if the primary sampling units were the same in all surveys.

> 2> To declare the combined dataset in Stata as a survey, I create a new > strata variable that doesn't overlap between the surveys (as suggested in > the previous thread). But how should I deal with the probability weights
> provided in each dataset?

See below.

> Suppose I assume that the sum of the weights in each country (countrysum) > represents the population, then can I just rescale each weight by (sum of
> weighs across all countries)/countrysum?

Don't assume: Check! If the weight sum in each country is approximately or exactly equal to the population size (number of firms), don't rescale. Use the weights as given.

(Modification: if you know the population sizes exactly and had <100% response, you might apply non-response adjustments. With SRS, the simplest is to create a new weight= N/n' where N is the known population size in the stratum and n' is the achieved sample size. For other methods, see section 8.5 of Sharon Lohr, Sampling: Design and Analysis, 1999 or 2010 editions, Brooks/Cole, Boston.)


> 3> I am running weighted regressions using the svy: regress command on the > combined dataset. If the sample size varies greatly between the surveys, > should I rescale each firm level variable in the regression by the sample
> size in that country or does svy take care of this?

Stata's survey commands will take care of it.



Steve

Steven J. 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/


© Copyright 1996–2018 StataCorp LLC   |   Terms of use   |   Privacy   |   Contact us   |   Site index