st: confidence intervals, saved results, pweights

[Ben Zipperer <benzipperer@gmail.com>]

confidence intervals of variable means in survey data with pweights.

As I understand it, -svy: mean- will show the confidence interval, but
only returns the variance and mean in its e() results. Is it
recommended that I simply use these e() results to calculate my own
confidence interval (to match the one reported but not saved by -svy:
mean-), or is there a command like -ci- that saves as macros the
confidence interval results with pweighted survey data?

Additionally, after -svy: mean- why can I display the elements of some
variance matrices but not others? For example,

. webuse fpc, clear

. svyset [pw=weight]

      pweight: weight
          VCE: linearized
  Single unit: missing
     Strata 1: <one>
         SU 1: <observations>
        FPC 1: <zero>

. svy: mean x
(running mean on estimation sample)

Survey: Mean estimation

Number of strata =       1          Number of obs    =       8
Number of PSUs   =       8          Population size  =      27
                                    Design df        =       7

--------------------------------------------------------------
             |             Linearized
             |       Mean   Std. Err.     [95% Conf. Interval]
-------------+------------------------------------------------
           x |   5.448148    .723725       3.73681    7.159486
--------------------------------------------------------------

. di el(e(V_srs),1,1)
.54734078

. di el(e(V),1,1)
matrix operators that return matrices not allowed in this context

thanks,
Ben
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