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st: Multistage sampling svyset


From   <James.Valcour@med.mun.ca>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Multistage sampling svyset
Date   Thu, 10 Jun 2010 16:03:20 -0230

I'm having a problem using the survey commands to analyzing a survey
that used a complex sampling design.  

Eleven communities were sampled (these were all the communities in the
study area).  Within each community households were randomly selected
from all available households.  Within each household one person was
randomly select from all members of the household that were eligible to
be in the survey (we had a list of everybody eligible in the house).

This is the code I used to set the data:

svyset houseid [pw=pwgt], strata(pi4) fpc(p_household) || _n,
fpc(p_person)

where
houseid is an identifier for the house in the community; a mix of the
community id number and the house number
pi4 is an identified for the community (1-11)
p_household is the probability of selection of the household in the
community
p_person is the probability of selection of the person in the household

The problem I'm getting is when I'm trying to estimate the proportion of
study with certain ailments.  I'm not getting confidence intervals
included in the estimates.  The message that is given is " Note: missing
standard errors because of stratum with single sampling unit."

I've tried other ways of specify the svyset command and tried
simplifying to the point of just assuming that household were sampled
but I get the same error.  (for the record here's that command "svyset
_n [pw=pwgt], strata(pi4) fpc(p_household)")

Any help would be appreciated,

Thanks!
James Valcour

--
Dr. James Valcour
Division of Community Health and Humanities
Faculty of Medicine
The Health Sciences Centre
Memorial University of Newfoundland
St. John's, NL, Canada
A1B 3V6
Tel:  709-777-2237
Fax: 709-777-7382
Email: james.valcour@med.mun.ca



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