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RE: st: Issue with multiple imputation -ICE-


From   René Wevers <rene@ricardis.tudelft.nl>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Issue with multiple imputation -ICE-
Date   Wed, 13 Feb 2008 17:17:55 +0100

Thanks for the replies so far.

The absolute number of employees does not have any zero values, as would be
expected. Thus it is still a complete mystery to me why negative values
appear after imputation.

I am now applying the -impute- command from Stata, which seems to perform
better. However, there are also dummy variables which need to be imputed.
This becomes a bit messy when applying the -impute- command since no
estimation technique can be selected (-logit- instead of -regress-). I am
now thinking of applying -impute- and then rounding the results for the
dummies, since these dummy variables are not very important for my analysis
(only for control). I know it isn't very pretty, but I don't see any other
(simple) solutions.

If anyone has any better ideas, I would gladly hear them.

Ow and naturally I will also run a standard analysis with listwise deletion.

Best regards,

René


-----Oorspronkelijk bericht-----
Van: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Namens Maarten buis
Verzonden: Wednesday, February 13, 2008 2:26 PM
Aan: statalist@hsphsun2.harvard.edu
Onderwerp: Re: st: Issue with multiple imputation -ICE-

--- René Wevers <rene@ricardis.tudelft.nl> wrote:
> For instance I am estimating missing variables for the full time
> equivalent (FTE) of employees of a company mainly based on the
> absolute number of employees. (Logically) the absolute number of
> employees is never below zero. Also when I run a regression between
> the FTE number and absolute number I get a highly significant 
> relation with positive coefficient and a positive constant estimates.
> Nevertheless when I run -ice-, the imputed values are extremely often
> (far) below zero (!!!).

Such a pattern can occur when the absolute number of employees have
received the value 0 when it actually should have been missing: than
you are extrapolating the number of FTEs for a company with 0
employees, which could very well be negative. 

Hope this helps,
Maarten

-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


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