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RE: st: RE: Re: Missing values test


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   RE: st: RE: Re: Missing values test
Date   Sun, 2 Dec 2007 18:07:16 +0000 (GMT)

--- Nick Cox <n.j.cox@durham.ac.uk> wrote:
> I don't find the idea of variables you don't have and that have no 
> connections with any variables you do have that compelling or
> congenial scientifically, but I bow to any superior wisdom here. 

By trying to be general, I am afraid I wasn't very clear. I was not
talking about the mythical unobserved variable ubiquitous in economics,
but about the missing values themselves. 

Say, we have a variable income, but some responents just choose not to
answer. MAR assumes that the probability of not answering should not
depend on the income of the individual. Problem for us is that we don't
know the income of those who choose not to answer, so we have no way of
knowing whether or not that is the case.

-- Nick Cox also wrote:
> I am concerned with the structure of missingness, not how to fix it. 

Knowing your data, including any structure of missingness seems sound
advise to me

-- Maarten
-- 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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