^idonepsu^ [varlist][^if^ exp] [^in^ range] [, Strata(varname) Psu(varname) Generate(newvarname) SWitch]
Description -----------
^idonepsu^ identifies strata that have only one PSU and, optionally, merges them into the largest strata. This command should be used with caution as the appropriate merge of strata depends on the sample design. This utility is intended for persons doing large secondary data analysis where they are uncertain of the sampling strategy and are, therefore, unable to identify the appropriate strata in which to merge. The merge is done in accord with the method suggested by the STATA 7 manual.
Options ------- ^varlist^ identifies the variables that are being used in the command that produces the singleton PSU warning. ^idonepsu^ uses the ^varlist^ only to identify missing values in variables and thus exclude the observation from the determination of singleton PSUs
^strata^ identifies the variable containing the strata. If no variable is specified, the variable that is currently set as the strata is used. For more information, see ^svyset^.
^psu^ identifies the variable containing the PSU. If no variable is specified, the variable that is currently set as the PSU is used. For more information, see ^svyset^.
^generate^ takes the strata with singleton PSU identified and then merges them into the strata with the most observations and renames the PSU to be unique within the merged strata. This is not the rigorous approach to dealing with singleton PSU, but it allows any inaccuracies to be absorbed by the strata with the most observations. The newly formed strata variable with the merged strata variable is put into ^newvarname^str. The identities of the strata that were merged and the strata into which They were merged are identified in the notes. Type -notes ^newvarname^str- The PSUs of the merged variable are also recoded to be unique and are placed In the new PSU, named ^newvarname^psu. The changes in PSU are identified in The notes for ^newvarname^psu. Type -notes ^newvarnam^psu-
^switch^ To run analyses, you will need to switch your psu and strata to the new psu and strata. Using the ^switch^ option merely automates this by issuing the commands -svyset strata ^newvarname^str- and the corresponding -svyset psu ^newvarname^psu-.
Example -------
If you want to know what strata have only one psu with the current settings:
idonepsu
If you would like to merge strata with singleton PSUs into the largest strata and call the new strata variable fixemstr and the new PSU variable fixempsu:
idonepsu, generate(fixem)
If you want to know what strata have only one psu with restrictions:
idonepsu depvar indvar1 indvar2 if smart==1, strata(str) psu(psuu)
If you would like to merge strata with singleton PSUs based on the restrictions into the largest strata and call the new strata variable slickstr and the new PSU variable slickpsu:
idonepsu depvar indvar1 indvar2 if smart==1, strata(str) psu(psuu) generate(slick)
If you would like to do the same as the above, but have the default psu and strata switched to the newly created psu and strata, simply type the ^switch^ option:
idonepsu depvar indvar1 indvar2 if smart==1, strata(str) psu(psuu) generate(slick) switch
Also see -------- Manual: [5s] tabulate On-line: ^help^ for ^svy^, ^svyset^
Author -------- Joshua H. Sarver, sarver@po.cwru.edu