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From |
Stas Kolenikov <skolenik@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: What does 'ssss' mean with replication dots? |

Date |
Sat, 7 Nov 2009 14:14:37 -0600 |

Note that you would probably need to modify your degrees of freedom when that happens. Does -svy jackknife- do that automatically? In Philip's example, it looks like the subpopulation is wholly contained in the second wave with 60 PSUs. On Fri, Nov 6, 2009 at 5:59 PM, Jeff Pitblado, StataCorp LP <jpitblado@stata.com> wrote: > Philip Burgess <philip.burgess.uq@gmail.com> is using -svy jackknife- and > noticed that there were 's' characters sprinkled in with the dots displayed > for each jackknife replicate: > >> I have two independent complex survey designs, one with 30 JK >> replicate weights (survey conducted in 1997), the other with 60 >> (survey conducted in 2007). >> >> I have combined these files in a manner similar to the Californian >> Health Interview Surveys - http://www.chis.ucla.edu/methodology.html >> (see the Methodology Paper on Examining Trends ... - this has detailed >> instructions regarding how to combine such data with STATA). >> >> So, my combined file has 90 replicate weights. >> >> I svyset with the following command: >> >> - svyset [pweight=mhsfinwt], jkrweight(wpm0101 - wpm0190, >> multiplier(1)) vce(jackknife) mse - >> >> When processing this design, for say, estimating propotions for the two surveys: >> >> - svy jackknife : proportion mhpsyo12, over(nsmhwb) >> (running proportion on estimation sample) >> >> Jackknife replications (90) >> ----+--- 1 ---+--- 2 ---+--- 3 ---+--- 4 ---+--- 5 >> .................................................. 50 >> ..........ssssssssssssssssssssssssssssss >> >> What does the 'ssss...' mean? > > 's' is one of those special codes like 'e' and 'n'; 'e' and 'n' are documented > with the -dots- option in -[SVY] svy jackknife-. > > 's' indicates that the corresponding replicate contributes nothing to the > variance estimate because the omitted PSU does not overlap with any > observations in the subpopulation. For example, in the delete-1 jackknife > this will occur when a PSU is in the estimation sample but is outside the > subpopulation sample. > > When replicate weight variables are -svyset-, this can only happen if the > values of the replicate weight variable are equal to the original sampling > weight within the estimation sample. > > Given Philip's -svyset- command, it appears that -- within the estimation > sample -- the last 30 replicate weight variables do not differ from the > -mhsfinwt- variable. > > In a future update, we will modify the help file for -svy jackknife- to > document the 's' character (like the 'e' and 'n' "dots"). > > --Jeff > jpitblado@stata.com > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ > -- Stas Kolenikov, also found at http://stas.kolenikov.name Small print: I use this email account for mailing lists only. * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**Re: st: What does 'ssss' mean with replication dots?***From:*jpitblado@stata.com (Jeff Pitblado, StataCorp LP)

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