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From | Rossella Verzulli <rossella.verzulli@unibo.it> |
To | "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |
Subject | st: RE: RE: psmatch2 vs attk |
Date | Wed, 26 Mar 2014 14:17:24 +0000 |
Joe Many thanks for your advice. However adding the common option in psmatch2 does not help to obtain the same results. I'm reporting the Stata output below. Best Rossella psmatch2 T, out(performance) kernel kerneltype(normal) pscore(mypscore) common ---------------------------------------------------------------------------------------- Variable Sample | Treated Controls Difference S.E. T-stat ----------------------------+----------------------------------------------------------- performance Unmatched | 99.7088608 100.653333 -.944472574 1.5097252 -0.63 ATT | 99.6129032 99.3059791 .306924102 1.993187 0.15 ----------------------------+----------------------------------------------------------- Note: S.E. does not take into account that the propensity score is estimated. psmatch2: | psmatch2: Common Treatment | support assignment | Off suppo On suppor | Total -----------+----------------------+---------- Untreated | 0 75 | 75 Treated | 17 62 | 79 -----------+----------------------+---------- Total | 17 137 | 154 . attk performance T, normal pscore(mypscore) comsup boot dots The program is searching for matches of each treated unit. This operation may take a while. ATT estimation with the Kernel Matching method --------------------------------------------------------- n. treat. n. contr. ATT Std. Err. t --------------------------------------------------------- 79 70 -1.568 . . --------------------------------------------------------- Note: Analytical standard errors cannot be computed. Use the bootstrap option to get bootstrapped standard errors. Bootstrapping of standard errors command: attk performance T , pscore(mypscore) comsup bwidth(.06) statistic: attk = r(attk) .................................................. Bootstrap statistics Number of obs = 154 Replications = 50 ------------------------------------------------------------------------------ Variable | Reps Observed Bias Std. Err. [95% Conf. Interval] -------------+---------------------------------------------------------------- attk | 50 -1.567504 -.2310363 2.32807 -6.245935 3.110928 (N) | -6.104194 3.185225 (P) | -5.293512 4.606492 (BC) ------------------------------------------------------------------------------ Note: N = normal P = percentile BC = bias-corrected ATT estimation with the Kernel Matching method Bootstrapped standard errors --------------------------------------------------------- n. treat. n. contr. ATT Std. Err. t --------------------------------------------------------- 79 70 -1.568 2.328 -0.673 --------------------------------------------------------- ________________________________________ Da: owner-statalist@hsphsun2.harvard.edu [owner-statalist@hsphsun2.harvard.edu] per conto di Joe Canner [jcanner1@jhmi.edu] Inviato: mercoledì 26 marzo 2014 15.11 A: statalist@hsphsun2.harvard.edu Oggetto: st: RE: psmatch2 vs attk Rossella, It's hard to say for sure without seeing more details, but I see that you are using the -comsup- option for -attk-, but you are not using the corresponding -common- option for -psmatch2-. Try adding that and see if it helps. Regards, Joe Canner Johns Hopkins University School of Medicine -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Rossella Verzulli Sent: Wednesday, March 26, 2014 9:58 AM To: statalist@hsphsun2.harvard.edu Subject: st: psmatch2 vs attk Dear Statalist I'm running the following commands to estimate the average treatment effects with the Kernel Matching method: psmatch2 T, out(performance) kernel kerneltype(normal) pscore(mypscore) attk performance T, normal pscore(mypscore) comsup Does anybody know why psmatch2 and attk produce slightly different output? I will very grateful for your advice. Best, Rossella * * 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/ * * 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/ * * 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/