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Re: st: impute with draws from random distribution

From   Maarten Buis <>
Subject   Re: st: impute with draws from random distribution
Date   Wed, 22 Jun 2011 11:07:30 +0200

On Wed, Jun 22, 2011 at 10:03 AM, D-Ta  wrote:
> The sample consists of of individuals (with covariates x1 and x2) who can
> either be participating in programm 1, programm 2, or be non-participants.
> The non-participants are my controll group. One of the control variables
> that I would like to condition on in a subsequent matching step is time to
> participation. By definition, time to participation is not observed for the
> non-participants. Hence, I would like to create hypothetical values in that
> variable for the group of non-participant. It is standard in the literature
> to randomly draw from the distribution of the participants.

It is absolutely wrong to try to impute values that for logical
reasons cannot exist. This is a case where the "dummy variable method"
for dealing with missing values is valid. See for example footnote 4
in Paul D. Allison (2002) Missing Data, Quantitative Applications in
the Social Sciences 136. Thousand Oaks: Sage.

Hope this helps,

Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
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