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Re: st: Missingness


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Missingness
Date   Tue, 28 Aug 2012 09:07:22 +0100

Your strategy isn't clear. Regardless of whether or how you use an
extra missingness variable, how do you expect Stata to treat the
missing values in the variables you already have?  Also, are the
ordinal predictors being treated as ordinal? Is the response ordinal
and does it include missing values too? One way forward is to treat
"missing" as just another category with its own code, but that would
seem to oblige you to treat such variables as nominal (in practice as
equivalent indicator variables) -- unless somehow you know that
"missing" always means "very big" or "very small" or "zero" and so can
be placed or one end or within the order.

Nick

On Tue, Aug 28, 2012 at 8:42 AM, Brendan Churchill
<Brendan.Churchill@utas.edu.au> wrote:

> I am using some ordinal variables, which have some numeric missing values, in a multilevel model. In some previous research, I have seen researchers include a 'Missing' independent variable in their model to account for some of the 'missingness' - or rather to control for the missing values, but I don't quite understand how to do it in Stata or even if that's a good way to do it. I've tried to make a binary variable in which the missing values are coded 1 and the rest of the values are coded 0 but the model rejects this because it's collinear.
>
> Is this how you do it? Or is there a variable for the entire data set that is created to account for all missing variables?
>
> I'd great appreciate any advice or assistance anyone out there could provide

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