John Sorkin
2010-Feb-17 21:07 UTC
[R] Characterizing overall agreement and the p values associated with the agreement. Kappa statistic
R 2.10.0
Windows XP
Please forgive a question that is not strictly speaking R centric
I have 24 raters, each of who characterizes 100 pictures into one of three
categories, A, B, or C. Each rater rates each picture twice in random order with
sufficient time between ratings so that the rater is unlikely to remember her,
or her prior rating.
data1<-matrix(nrow=24,ncol=2)
data1[,1]<-rater1Firstvalue
data1[,2]<-rater1Secondtvalue
data2<-matrix(nrow=24,ncol=2)
data2[,1]<-rater2Firstvalue
data2[,2]<-rater2Secondtvalue
.
.
.
data24<-matrix(nrow=24,ncol=2)
data24[,1]<-rater24Firstvalue
data24[,2]<-rater24Secondtvalue
I would like to determine the within-observer agreement. For each of the 24
raters, I am using kappam.fleiss to assess agreement:
Kappa[1,"Kappa"]<-kappam.fleiss(data1, exact = TRUE, detail =
TRUE)$value
Kappa[2,"Kappa"]<-kappam.fleiss(data2, exact = TRUE, detail =
TRUE)$value
.
.
.
Kappa[24,"Kappa"]<-kappam.fleiss(data24, exact = TRUE, detail =
TRUE)$value
Similarly I isolate each of the 24 p values:
Kappa[1,"Kappa"]<-kappam.fleiss(data1, exact = TRUE, detail =
TRUE)$p.value
Kappa[2,"Kappa"]<-kappam.fleiss(data2, exact = TRUE, detail =
TRUE)$p.value
.
.
.
Kappa[24,"Kappa"]<-kappam.fleiss(data24, exact = TRUE, detail =
TRUE)$p.value
Can characterize the overall agreement and p value as the mean of the 24 kappa
values and 24 p values, i.e.
mean(kappa)
Thanks,
John
John David Sorkin M.D., Ph.D.
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing)
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