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

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: ICE: Combining proportions using Rubin's rules via mim |

Date |
Sat, 1 Jan 2011 22:42:09 -0600 |

On Sat, Jan 1, 2011 at 12:53 PM, Leslie Phillips <leslie.phillips@gmail.com> wrote: > I am using Patrick Royston's ICE to multiply impute data that will be > used to calculate proportions. I have calculated my proportions on > the m imputed datasets which ICE appends into one dataset. I now want > to combine my proportions using Rubin's rule. It is my first > experience with MICE/ICE and I am a basic to less-than-basic Stata > user so I am stumbling through this a bit but my read of it is that > the overall estimate is the average of the individual estimates (in my > case proportions). It seems ICE will do this for me as follows: > 1) I use ice to carry out m imputations > 2) I calculate my proportion ("myprop") in the appended dataset which > calculates m proportions for each _mi > 3) Here's where it gets tricky for me, is it correct to use the mim > combine command as below to get the appropriately combined proportions > and a standard error that accounts for both the within and between > imputation variance a la Rubin? And if so, I should just repeat this > for each _mi? > > mim, cat(combine) est(_b[myprop]) se(_se[myprop]) : mean myprop if _mi==1 -mim- is aware of the structure created by -ice-, so the -if- condition is redundant (and, in fact, inappropriate). Also, since -mim- knows that -mean- is an estimation command, you don't need to specify the -category()- option. So your very slim syntax will be mim : mean myprop and it will invoke Rubin's combination rules. (Of course you still need to have a good imputation model and a reasonable number of imputations to get result you can trust.) -- 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**:**st: ICE: Combining proportions using Rubin's rules via mim***From:*Leslie Phillips <leslie.phillips@gmail.com>

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