Dear Listers
I just installed Stata version 9 and I am re-running some analysis that I
previously used Stata 8.
The survey data (n=6,333) I am using comes from a multistage design, but I
only have information on strata (8) and PSU (403) and I treat this data as
a single stage clustered design. There are a few PSU with one observations
only.
However, subsequent 'svy' estimates show the number of PSUs as 6,333
instead of 403. It did not happen in Stata 8.
First I 'surveyset' data by:
. svyset psu [pw=wt], strata(stateur);
pweight: wt
VCE: linearized
Strata 1: stateur
SU 1: psu
FPC 1: <zero>
Then I 'svvydes' to see whether the 'svyset' defined the psu and strata
correctly .
. svydes
Survey: Describing stage 1 sampling units
pweight: wt
VCE: linearized
Strata 1: stateur
SU 1: psu
FPC 1: <zero>
#Obs per Unit
----------------------------
Stratum #Units #Obs min mean max
-------- -------- -------- -------- -------- --------
1 111 1972 3 17.8 73
2 115 1725 2 15.0 42
3 58 1032 1 17.8 69
4 41 519 3 12.7 30
5 44 656 3 14.9 44
6 14 187 5 13.4 34
7 7 95 7 13.6 22
8 13 147 5 11.3 23
-------- -------- -------- -------- -------- --------
8 403 6333 1 15.7 73
However, when estimating means, the number of PSUs is shown as 6,333.
. svy: mean violence
(running mean on estimation sample)
Survey: Mean estimation
Number of strata = 8 Number of obs = 6333
Number of PSUs = 6333 Population size = 6.9e+06
Design df = 6325
--------------------------------------------------------------
| Linearized
| Mean Std. Err. [95% Conf. Interval]
-------------+------------------------------------------------
violence | .0712806 .0039479 .0635415 .0790198
--------------------------------------------------------------
I must have overlooked something. But I could not figure it out what is
going on.
Any assistance will be greatly appreciated.
Thanking you in advance.
Pramod Adhikari
------------------------------------------------------------------------------------------------
Free publications and statistics available on www.abs.gov.au
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
