Richard Williams <[email protected]> suggested the following code:
<snip>
. webuse nhanes2f.dta
. version 8.2: svyset [pw=finalwgt], clear
pweight is finalwgt
. pwcorr female black height [aw=finalwgt], sig
| female black height
- -------------+---------------------------
female | 1.0000
|
|
black | 0.0157 1.0000
| 0.1102
|
height | -0.7041 -0.0041 1.0000
| 0.0000 0.6800
|
. corr_svy female black height, sig
Survey Correlation
pweight: finalwgt
Strata: <one>
PSU: <observations>
Number of observations: 10337
| female black height
- -------------+------------------------------------
female | 1.0000
|
|
black | 0.0157 1.0000
| 0.1741
|
height | -0.7041 -0.0041 1.0000
| 0.0000 0.7185
- --------------------------------------------------
Key: Estimated Correlation
Significance Level
Exact same correlation estimates, but different estimates of the
significance levels. It isn't obvious from these particular printouts, but
in general specifying pweights produces the same results as specifying
aweights and robust.
All very interesting and as I would expect, but why is version 8.32 of
svyset needed? And why do the correlations change if I use
version 9?
. webuse nhanes2f.dta
. svyset [pw=finalwgt], clear
pweight: finalwgt
VCE: linearized
Strata 1: <one>
SU 1: <observations>
FPC 1: <zero>
. corr_svy female black height, sig
Survey Correlation
pweight: <none>
Strata: <one>
PSU: <observations>
Number of observations: 10337
| female black height
-------------+------------------------------------
female | 1.0000
|
|
black | 0.0099 1.0000
| 0.3115
|
height | -0.6987 0.0057 1.0000
| 0.0000 0.5592
--------------------------------------------------
Key: Estimated Correlation
Significance Level
=========================
Paul T Seed
King's College London,
Division of Reproductive Health, Endocrinology and Development
St Thomas' Hospital,
Lambeth Palace Road,
London SE1 7EH
Funded by the Wellcome Trust & Tommy's the Baby Charity
([email protected])
tel (+44) (0) 20 7188 3642
fax (+44) (0) 20 7620 1227
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