Peter, Thanks for your reply. To perform the analysis in R, I used the table format suggested in the book by Everitt & Hothorn, whereas in SPSS the analysis was performed directly from the 2 variables, rather than using count data.
There is still something I don't understand - I tried to replicate the syntax from your e-mail but my computer just kept waiting - what am I still doing wrong? mctest <- as.table(matrix(c(128,29,331,430), ncol =2, dimnames = list(group=c("preMHT","postMHT"), assault=c("yes","no")))) > d <- read.table(stdin()) 0: mcnemar.test(as.matrix(d),correct=F) 1: Thanks again Bob At 10:52 PM 26/12/2006 +0100, Peter Dalgaard wrote: >Bob Green wrote: >>Hello, >> >>I am hoping someone can clarify why I might obtain a quite different >>value in R & SPSS for a McNemar test I ran. >> >>Firstly, here is the R syntax & output >> >> >>R OUTPUT >> >> > mctest <- as.table(matrix(c(128,29,331,430), >>+ ncol =2, dimnames = list(group=c("preMHT","postMHT"), >>+ assault=c("yes","no")))) >> >> > mctest >> assault >>group yes no >> preMHT 128 331 >> postMHT 29 430 >> >> > mcnemar.test(mctest,correct=F) >> >> McNemar's Chi-squared test >> >>data: mctest >>McNemar's chi-squared = 253.3444, df = 1, p-value < 2.2e-16 >> >> >>SPSS OUTPUT >> >>The same data was inputted in SPSS. Regarding the first table SPSS >>generated - it lists the number of cases in each combination of >>categories. The diagonal contains the number of cases with the same >>response on both variables, while the off diagonal contains cases that >>have different responses on the 2 variables. The overall chisquare value >>is much lower than the value obtained using R, though still significant. >> >> >>pre02 & post02 >> >>pre02 post02 >> >> 0 1 >>0 311 20 >>1 119 9 >> >> >>Test Statistics(b) >> >> pre02 & post02 >> >>N 459 >>Chi-Square(a) 69.094 >>Asymp. Sig. .000 >> >>a Continuity Corrected >>b McNemar Test >> >> >>Any assistance is much appreciated, >> >Well, you can't expect R to give the correct result if you feed it the >wrong matrix, can you? > >>d <- read.table(stdin()) > >0: 0 1 > >1: 0 311 20 > >2: 1 119 9 > >3: >>d > > X0 X1 > >0 311 20 > >1 119 9 > >>mcnemar.test(as.matrix(d),correct=F) > > McNemar's Chi-squared test > >data: as.matrix(d) >McNemar's chi-squared = 70.5108, df = 1, p-value < 2.2e-16 > >>mcnemar.test(as.matrix(d),correct=T) > > McNemar's Chi-squared test with continuity correction > >data: as.matrix(d) >McNemar's chi-squared = 69.0935, df = 1, p-value < 2.2e-16 > > > >>Bob Green >> >>______________________________________________ >>R-help@stat.math.ethz.ch mailing list >>https://stat.ethz.ch/mailman/listinfo/r-help >>PLEASE do read the posting guide http://www.R-project.org/posting-guide.html >>and provide commented, minimal, self-contained, reproducible code. >> ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.