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From |
Miguel Dorta <[email protected]> |

To |
[email protected] |

Subject |
Re: st: how OK is -mi estimate, errorok- ? |

Date |
Tue, 29 Oct 2013 16:01:57 -0500 |

Stas Kolenicov <[email protected]> asks about the -errorok- option of the -mi estimate- command: >I am trying to circumvent an issue that -proportion- sometimes return >what looks like a reasonable zero estimate (just because the data are >like that), but -mi estimate- seems to have problems with it, even >with -errorok- option: > >sysuse auto, clear >mi set wide >mi register imputed rep78 >mi register regular weight >mi impute chained (pmm) rep78, add(3) >mi estimate : proportion rep78, over( foreign ) >mi estimate, errorok : proportion rep78, over( foreign ) >mi estimate, noisily : proportion rep78, over( foreign ) > >It's not that bad in my data, but some proportions are really small in >one of the subpopulations, and they get zero imputed counts every now >and then. But most imputation would produce the full vector of >coefficients. Nevertheless, -errorok- fails to handle that. When an estimation command used with -mi estimate- executes with an error in at least one of the imputations, -mi estimate- stops and flags the problem. To proceed with estimation and discard the offending imputations, you can use the -errorok- option; also see -help mi estimate-. In Stas's example, the -proportion- command executes successfully on all imputations. The error message that Stas receives: mi estimate: no observations in some imputations This is not allowed. To identify offending imputations, you can use mi xeq to run the command on individual imputations or you can reissue the command with mi estimate, noisily r(498); is issued because of -mi estimate-'s internal checks of the consistency of results from all of the imputations. The -errorok- option has no control over these checks. The inconsistency between imputation results in Stas's example is caused by the fact that the -rep78- variable has no observations in some of its categories in some of the imputations when it is cross-classified with the -foreign- variable. If -rep78- had no observations in the same categories across imputations, -mi estimate- would proceed without error and report results for all of the categories which contain observations. One solution is to use -mi xeq- to identify the offending imputations and perform MI estimation using only non-offending imputations. You can specify the list of imputations in -mi estimate-'s option -imputations()-. . mi xeq: proportion rep78, over(foreign) (output omitted) The output from -mi xeq- indicates that the second imputation is the offending imputation. We can then perform MI estimation using only imputations 1 and 3: . mi estimate, imputations(1 3): proportion rep78, over(foreign) (output omitted) -- Miguel [email protected] * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

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