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RE: st: RE: Imputed Missing Values with Uvis


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: RE: Imputed Missing Values with Uvis
Date   Fri, 25 Feb 2005 01:14:11 -0000

This is now a matter of taste to be 
argued out with Patrick Royston, 
the author of -uvis-, not myself.
I am copying this to him, as he 
is not a member of Statalist. 

That said, I think his decision 
is correct, as it makes a distinction 
between imputation and whatever else one may 
decide is sensible, and it follows  
general Stata philosophy of doing just
one thing properly. It's also closer 
to the philosophy of -predict-, which 
won't make a prediction when not instructed 
to, even if there is a possible 
non-missing prediction. 

Otherwise said, the job of an imputation 
program is to impute, not to remind 
you of what you may happen to know. 

Nick 
n.j.cox@durham.ac.uk 

> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of Richard
> Williams
> Sent: 25 February 2005 01:00
> To: statalist@hsphsun2.harvard.edu
> Subject: RE: st: RE: Imputed Missing Values with Uvis
> 
> 
> At 11:36 PM 2/24/2005 +0000, Nick Cox wrote:
> >No doubt this is what is often
> >wanted. But the help for -uvis-
> >is explicit:
> >
> >Note that uvis will not impute observations for which
> >a value of a variable in xvarlist is
> >missing. Only complete cases within xvarlist are used.
> 
> I still find that unclear and not what I would expect!  I 
> agree that it 
> cannot and should not impute observations when one or more 
> x's have missing 
> values.  But, it should not be imputing in the first place if 
> y is not 
> missing, it should just plug in the observed value of y. As 
> it stands, the 
> program can actually create more missing data than was there 
> in the first 
> place.  I suspect this is an unintended design flaw; at least 
> I cannot 
> think of any reason why you would want it to behave this way.

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