Hi,
I am working on a data from a 2 stage survey design with 2 stratum. When I calculate the mean of hhsize, the standard error is missing as shown below.
svy: mean hhsize
(running mean on estimation sample)
Survey: Mean estimation
Number of strata = 2 Number of obs = 5964
Number of PSUs = 194 Population size = 16041309
Design df = 192
--------------------------------------------------------------
| Linearized
| Mean Std. Err. [95% Conf. Interval]
-------------+------------------------------------------------
hhsize | 4.656919 . . .
--------------------------------------------------------------
Note: missing standard error because of stratum with single
sampling unit.
As per http://www.stata.com/support/faqs/stat/stratum.html, I check my data using svydes hhsize and find the following:
Survey: Describing stage 1 sampling units
pweight: weight
VCE: linearized
Single unit: missing
Strata 1: rural
SU 1: psu
FPC 1: npsu
Strata 2: <one>
SU 2: ssu
FPC 2: nssu
Strata 3: <one>
SU 3: hh
FPC 3: nhh
#Obs with #Obs with #Obs per included Unit
#Units #Units complete missing ----------------------------
Stratum included omitted data data min mean max
-------- -------- -------- -------- -------- -------- -------- --------
1 136 0 4241 0 16 31.2 39
2 58 0 1723 0 16 29.7 32
-------- -------- -------- -------- -------- -------- -------- --------
2 194 0 5964 0 16 30.7 39
------------------
5964
Why are the standard errors missing when both stratum have more than one sampling unit and there are no missing observations.
Thanks for your help
Cheers
Michael
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