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st: Re: dropped cases using mi impute mvn


From   exp12 <exp12@psu.edu>
To   statalist@hsphsun2.harvard.edu
Subject   st: Re: dropped cases using mi impute mvn
Date   Wed, 20 Oct 2010 18:21:58 -0700 (PDT)

I knew it had to be something simple, but didn't pick this up working through
the manual.  Much thanks!
- Eric

On Wed, Oct 20, 2010 07:41 PM, "Wesley D. Eddings, StataCorp [via Statalist]"
<ml-node+5657023-2147369293-298144@n2.nabble.com> wrote:
>
>
>Eric <<>> asked about differences between the numbers of observations

>in imputations created by -mi impute mvn-:

>
>> The relevant lines of code are:

>>

>> mi set mlong

>   (snip)



>

>> mi impute mvn y1 y2 y3 y4 y5 y6  dummy1 dummy2 = x1 x2, add(3)

>>

>> This runs without error, but as you can see below, the number of cases is

>> wrong for the three imputed data sets.  Somehow 730 cases are dropped.

>>

>> .	tab	_mi_m

>>

>> 		_mi_m       Freq.	Percent	Cum.

>>					

>> 		0       2,812	31.04	       31.04

>>		1       2,082	22.99	       54.03

>>		2       2,082	22.99        77.01

>>		3       2,082	22.99	      100.00

>>					

>>	Total         9,058	       100.00


>The -mi- commands are behaving as intended.  The -mi- commands offer several

>storage styles, and Eric in his -mi set- command chose the -mlong- ("marginal

>long") style, which stores only the 2082 incomplete observations in the

>imputations.  The 730 complete observations are not repeated in the imputations

>and are stored only in the original data.

>
>Eric mentioned -ice-, which always repeats the complete observations in the

>imputations.  The official -mi- style that repeats the complete observations is

>-flong- ("full long").  All -mi- commands work regardless of style, but if Eric

>would prefer to work in the -flong- style, he may convert to it with the -mi

>convert- command.

>
>For more information on -mi- styles, Eric may type

>
>     . help mi glossary

>     . help mi styles

>
>-- Wes

><>

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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Eric Plutzer, Professor of Political Science
     and Academic Director, Survey Research Center
The Pennsylvania State University




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