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st: Different confidence intervals from proportions and tabulates (also in survey)
Hi. I have been running survey proportions and observing results with
negative confidence intervals (which doesn't make sense). When I use
survey tab (with column percent, se and ci) I get the same point
estimates and standard errors but different 95% confidence intervals. I
assume this is an issue with the proportion calculations using "Binomial
Wald" for confidence intervals.
I checked the survey manual and have not been able to find why:
Paste the following command to see my dilemma:
webuse nhanes2b, clear
svy: proportion race
svy: tab race, ci se
The results show the same point estimates and standard errors (with
rounding) but different CI's. As mentioned, for my data, I get some
negative CI's for svy: proportions commands but not for the svy:
tabulate commands. My ultimate concern is being able to automatically
extract the CORRECT estimates to excel (from using matrix e(b) and e(V)
- and calculating 95% CI from square-root of e(V) *1.96).
I am using the latest version of Stata 9.2, on Windows XP.
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