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From | Ricky Lim <ricky.lim12345@gmail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | st: Propensity score matching: Must all treated samples have a counterfactual? |
Date | Fri, 16 Aug 2013 14:57:09 +0100 |
Dear Statalisters, I ran running propensity score matching using -pscore- and would like to do radius & nearest neighbour matching (nearest 3 within +- x score). 15 out of 20 of my treated samples have more than 3 counterfactuals within 0.05 scores, whereas the remaining 5 have 1 or none. Their propensity scores are at the extreme and I would need to increase the range to +-0.5 before they will have 3 counterfactuals each. My questions are: 1. Must every treated sample have a counterfactual / control? 2. Is a radius of 0.5 score too wide? Is it be acceptable to use the nearest 3 within 0.5 score? Any advice is deeply appreciated. Thank you very much in advanced. Regards, Ricky * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/