st: strata with single sampling units

[frone@ria.buffalo.edu]

Hello,

I'm trying to analyze a national data set using Stata 11.  However, the 
following set up

svyset psu [pweight=weight], strata(stratum);

resulted in no variance estimates because of many strata with only 1 PSU. 

When I went back to the documentation it is stated that the study 
used a multistage stratified design in which primary sampling units
(PSUs) were stratified according to certain sociodemographic criteria. The 
sampling
frame for housing units is the Census 2000/2001 Supplementary Survey 
(C2SS) and that
for group quarters is the Census 2000 Group Quarters Inventory. The C2SS 
sample of
655 PSUs was selected at the first stage, including 401 self-representing 
(SR) and 254
non-self-representing (NSR) PSUs. All SR PSUs were selected with 
certainty. For the
NSR sample, two PSUs were selected per stratum, with probability 
proportional to the
size of the estimated 1996 population of the stratum.  NOTE: Sample was 
included from each of the 655 PSUs.
However, to prevent potential respondent disclosure, some PSUs were 
collapsed so that the final
data file shows 435 PSUs, 305 being SR and 130 being NSR.

So there are 305 strata with one PSU.  Final sample is 43,093.

Would I be safe in assuming that one would use weight and PSU, and ignore 
strata in this case?  No other design variables are provided.  Doing 
things this way seems to replicate SEs in the published tables  -- at 
least the few I tried to replicate. 

Mike Frone 

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