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Hi,
This is my first posting and I apologise if similar questions have
been asked before.
I have run these R codes (codes mostly taken from Matt Bogart blog).
My question would be:
1) (see the lowermost of the codes) Which model specification is the
'best' the describe the adjusted/matched predictive effect of 'treat'
upon 're78'?
2) What is the difference between the linear combination of 'treat +
pscore' against 'treat +
age+educ+black+hispan+married+nodegree+re74+re75' when both are using
the matched data generated by 'match.data'
###################################
library(MatchIt)
data1<-lalonde
#matching
m.out1<-matchit(treat~age+educ+black+hispan+nodegree+married+
re74+re75,data=data1,method = 'nearest',
distance = 'logit')
# create matched data based on matchit, giving the output ps as pscore
m.data1<-match.data(m.out1,distance='pscore')
# generate propensity score manually
m.data2<-lalonde
head(m.data2)
ps.mod<-glm(treat~age+educ+black+hispan+married+
nodegree+re74+re75,data=m.data2,family = binomial(link='logit'))
summary(ps.mod)
#predict for prosp score
head(m.data2)
m.data2$psore<-fitted(ps.mod)
head(m.data2)
dim(m.data2)
#do models
mod.reg<-lm(re78~treat+age+educ+black+hispan+married+nodegree+re74+re75,data
= lalonde)
mod.ps1<-lm(re78~treat+age+educ+black+hispan+married+nodegree+re74+re75,data
= m.data1)
mod.ps11<-lm(re78~treat+pscore,data = m.data1)
mod.ps2<-lm(re78~treat+age+educ+black+hispan+married+nodegree+re74+re75,data
= m.data2)
#restrict to ps between 0.1 to 0.9
m.data3<-m.data2[m.data2$psore>=0.1 & m.data2$psore<=.9,]
mod.ps3<-lm(re78~treat+age+educ+black+hispan+married+nodegree+re74+re75,data
= m.data3)
summary(mod.reg);summary(mod.ps1);summary(mod.ps11);summary(mod.ps2);summary(mod.ps3)
#####################
Thank you
Kamarul
--
Dr. Kamarul Imran Musa,
M.D. M.Community.Med.
Associate Professor (Epidemiology and Biostatistics) &
Public Health Physician
Dept of Community Medicine
School of Medical Sciences
16150 Universiti Sains Malaysia, Kbg Kerian
Kelantan
Thomson Reuters researchID: http://www.researcherid.com/rid/G-4864-2010
Google-scholar:
http://scholar.google.co.uk/citations?user=aZyayMgAAAAJ&hl=en&authuser=1
blog: http://designdataanalysis.wordpress.com
email : drkamarul(a)usm.my , k.musa(a)lancaster.ac.uk
