Statalist The Stata Listserver


[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

st: Single stage design and PSU - STATA version 9


From   pramod.adhikari@abs.gov.au
To   statalist@hsphsun2.harvard.edu
Subject   st: Single stage design and PSU - STATA version 9
Date   Fri, 31 Mar 2006 17:01:54 +1100

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/



© Copyright 1996–2020 StataCorp LLC   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index