Stata The Stata listserver
[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

st: adjustment for complex survey design

From   "Liang, Su-Ying" <>
Subject   st: adjustment for complex survey design
Date   Fri, 7 Oct 2005 12:09:35 -0700

We are conducting analyses using National Health Interview Survey and Medical Expenditures Panel Survey.  Both are nationally representative surveys.  We use the survey commands in STATA to adjust for complex survey design and have to decide how to deal with the problem with single psu.  We understand that it is important to adjust for all three levels of survey design (weights, PSUs, and strata) in order to obtain correct variance and standard errors.  However, we are wondering what the statistical implications are (magnitude and direction of standard errors, in particular) if we only adjust for weights and PSUs but not strata.  Per the Stata manual, the variance estimates are based only on computations at the primary sampling-unit level and do not require information about the secondary sampling units.  We thus had considered the loss of efficiency without adjusting for strata might have little impact on the variance estimates or standard errors.

We ran bivariates analyses with and without adjusting for strata.  For some analyses, results of the Pearson chi-square test were similar.  However, for other analyses, results were very different, e.g., analysis without adjusting for strata is not significant (p=0.16) while analysis adjusting for strata is highly significant (p<0.001).

We are wondering whether it has been examined or determined how the results may or may not vary without or without adjusting for strata.  Does it depend on the type of analyses (bivaraite or regression), sample size, or sub-group analyses? 

We would greatly appreciate your thoughts on this issue.


Su-Ying Liang, Ph.D.
University of California San Francisco
3333 California St. Suite 420 Box 0613
San Francisco, CA 94143 (fedex 94118)
Voice (415) 514-0457
Fax (415)- 502-0792

*   For searches and help try:

© Copyright 1996–2017 StataCorp LLC   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index