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...ssignment is not random,so the selection-bias exists.Under this condition,what's the best way to estimate the treatment effect? I know that if the treatment is binary,I can use propensity score matching using MatchIt package.But what about multinomial? Maybe one way is the method proposed by Imbens,2000,The role of the propensity score in estimating dose-response functions,Biometrika,87:706-710.But I can't find any R function to do the task.So I hope the lister can give me some suggestions. Thank you in advance! -- ?????? Department of Sociology Fudan University

Hi, I already have matched samples, which were matched using different software. I need to calculate Abadie-Imbens standard errors, together with the average treatment effect. I know that the Matching package enables me to calculate these after a Matching procedure, but is there any way to do it on already matched samples, which were not produce by the Match function? Many thanks, Louise. -- View this messag...

To anyone who uses the Match() function in the Matching library... How do you go about deciding how many matches you will use? With my data, my standard errors generally get smaller if I use more matches. Speaking of standard errors, when correcting for heteroscedasticity, how many matches do you use (this is the Var.cal option). It seems to me that it might make sense to use the same number