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) Confidentiality Statement: This email message, including any attachments, is for th...{{dropped:6}}