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Re: st: mi impute chained error messages


From   "JVerkuilen (Gmail)" <jvverkuilen@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: mi impute chained error messages
Date   Mon, 22 Oct 2012 09:11:41 -0400

On Sun, Oct 21, 2012 at 8:18 PM, chong shiauyun <shiauyun416@hotmail.com>wrote:

> Hi there
> I was doing a dryrun for my imputation model using 'mi impute chained". My
> outcome of interest is Total IQ, which is a continous variable. I censored
> the score of Total IQ in between 45 and 151 by generating a lower limit
> ll(lTIQ) and a upper (uPIQ). I was also thinking to put verbal IQ and
> performance IQ, which are also censored, into the imputation model. In my
> imputation model, I used different methods including mlogit, logit,
> intereg, and regression. I also inserted a few interaction terms, which are
> new variables that I created. When I specify (intreg) for Total IQ, verbal
> IQ, and Performance IQ, I received error message that interval regression
> can only take one new variable. I tried again with only Total IQ in my
> interval regression, but Stata error message said the ll and ul are
> invalid. Can anyone please help?
>

I'd simplify things substantially. You have A LOT going on here, so
much it's not really possible to do troubleshooting. Cut down to
simple imputation models and build up so you can see where things run
into trouble. These intermediate models don't need to be realistic,
but should be moving in the direction of your final model.

For instance, IQ is probably going to naturally censor between those
cuts in any typical population, so you can probably simplify just by
switching to a linear regression.

By the way I highly recommend getting the new -midiagplots- command,
which is simple to use and of great help diagnosing imputation models'
performances. You may not need a super complex MI model to get
reasonable imputations. I hope this gets incorporated into the base
product in the future!
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