Matchit May 2015

matchit@lists.gking.harvard.edu

5 participants
3 discussions

SD Control vs SD Treated in summary.matchit with standardize = TRUE

by Philipp Doebler

Dear MatchIt Mailing List, when I calculated some summary statistics to compare means before and after matching, I used the standardized = TRUE option to obtain standardized mean differences. However, to my surprise, the output shows that the standard deviation in the control group is used for standardization (where I felt the SD of the treatment group was more appropriate but I can live with that). You can produce the output I am referring to via: summary(matchit(formula = treat~re74+re75+ black+hispan+educ+age, data = lalonde), standardized = TRUE) As I was unsure which SD was used to standardize, I dug in the code and noticed, that in the MatchIt:::qoi function the SD is actually calculated from the treatment group, i.e. I am almost sure that in the code of qoi, the SD of the treated is calculated. I am using a very recently built version of Matchit from CRAN but the underlying code seems not to have been updated since 2013. Has this been addressed/fixed in the meantime? With kind wishes, Philipp Doebler Version information: Package: MatchIt Version: 2.4-21 Date: 2013-06-26 Date/Publication: 2013-06-28 00:55:57 Built: R 3.2.0; ; 2015-05-18 19:26:11 UTC; unix

8 years, 11 months

Standardized mean difgerence

by Gianluca Bonitta

Dear List good morning I have a question How is the standardize mean difference in full matching method for both continuous and categorical variables? In unmatched sample if I use like standardized mean difference for categorical variables this formulae: m <- pcontrol-ptrt # where p stay for percentual a<- ptrt*(1-ptrt) + pcontrol*(1-pcontrol) z <- m/sqrt(a/2) the results match with matchit... but I' m not able to caluculate standardized mean difference into full matched sample where there are the weights Can You so gentle to help me Thank You in advance Bonitta Gianluca

8 years, 12 months

Getting ATT and ATE estimates after calling MatchIt

by Riley, Barth B

Dear list Is there a way to estimate the ATT and ATE effect sizes after calling MatchIt? I am using MatchIt to perform optimal matching for causal inference. Thanks in advance Barth Riley

9 years

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Matchit May 2015