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From | D-Ta <altruist81@gmx.de> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: impute with draws from random distribution |
Date | Wed, 22 Jun 2011 11:32:44 +0200 |
Otherwise, the start date cannot be used as a control variable in the matching approach. With your advice to generate dummies for missing values (and to control for those) you cant (by definition) reach common supported between the treated and the comparison group.
Am 22.06.2011 11:07, schrieb Maarten Buis:
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 -------------------------- Maarten L. Buis Institut fuer Soziologie Universitaet Tuebingen Wilhelmstrasse 36 72074 Tuebingen Germany http://www.maartenbuis.nl -------------------------- * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/
* * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/