Hello David,Thank you for your answer. Do you know then what does the "mcnemar.test" do in the case of a 3*3 table ? Because the results for the simple example I gave are rather different (P value of 0.053 VS 0.73)
In case the mcnemar can't really handle a 3*3 matrix (or more), shouldn't there be an error massage for this case? (if so, who should I turn to, in order to report this?) Thanks again, Tal On Sun, Jul 19, 2009 at 3:47 PM, David Freedman <3.14da...@gmail.com> wrote: > > There is a function mh_test in the coin package. > > library(coin) > mh_test(tt) > > The documentation states, "The null hypothesis of independence of row and > column totals is tested. The corresponding test for binary factors x and y > is known as McNemar test. For larger tables, StuartÂ’s W0 statistic (Stuart, > 1955, Agresti, 2002, page 422, also known as Stuart-Maxwell test) is > computed." > > hth, david freedman > > > Tal Galili wrote: > > > > Hello all, > > > > I wish to perform a mcnemar test for a 3 by 3 matrix. > > By running the slandered R command I am getting a result but I am not > sure > > I > > am getting the correct one. > > Here is an example code: > > > > (tt <- as.table(t(matrix(c(1,4,1 , > > 0,5,5, > > 3,1,5), ncol = 3)))) > > mcnemar.test(tt, correct=T) > > #And I get: > > McNemar's Chi-squared test > > data: tt > > McNemar's chi-squared = 7.6667, df = 3, p-value = *0.05343* > > > > > > Now I was wondering if the test I just performed is the correct one. > >>From looking at the Wikipedia article on mcnemar ( > > http://en.wikipedia.org/wiki/McNemar's_test), it is said that: > > "The Stuart-Maxwell > > test<http://ourworld.compuserve.com/homepages/jsuebersax/mcnemar.htm> > > is > > different generalization of the McNemar test, used for testing marginal > > homogeneity in a square table with more than two rows/columns" > > > >>From searching for a Stuart-Maxwell > > test<http://ourworld.compuserve.com/homepages/jsuebersax/mcnemar.htm> > > in > > google, I found an algorithm here: > > > http://www.m-hikari.com/ams/ams-password-2009/ams-password9-12-2009/abbasiAMS9-12-2009.pdf > > > >>From running this algorithm I am getting a different P value, here is the > > (somewhat ugly) code I produced for this: > > get.d <- function(xx) > > { > > length1 <- dim(xx)[1] > > ret1 <- margin.table(xx,1) - margin.table(xx,2) > > return(ret1) > > } > > > > get.s <- function(xx) > > { > > the.s <- xx > > for( i in 1:dim(xx)[1]) > > { > > for(j in 1:dim(xx)[2]) > > { > > if(i == j) > > { > > the.s[i,j] <- margin.table(xx,1)[i] + margin.table(xx,2)[i] - > > 2*xx[i,i] > > } else { > > the.s[i,j] <- -(xx[i,j] + xx[j,i]) > > } > > } > > } > > return(the.s) > > } > > > > chi.statistic <- t(get.d(tt)[-3]) %*% solve(get.s(tt)[-3,-3]) %*% > > get.d(tt)[-3] > > paste("the P value:", pchisq(chi.statistic, 2)) > > > > #and the result was: > > "the P value: 0.268384371053358" > > > > > > > > So to summarize my questions: > > 1) can I use "mcnemar.test" for 3*3 (or more) tables ? > > 2) if so, what test is being performed ( > > Stuart-Maxwell< > http://ourworld.compuserve.com/homepages/jsuebersax/mcnemar.htm>) > > ? > > 3) Do you have a recommended link to an explanation of the algorithm > > employed? > > > > > > Thanks, > > Tal > > > > > > > > > > > > -- > > ---------------------------------------------- > > > > > > My contact information: > > Tal Galili > > Phone number: 972-50-3373767 > > FaceBook: Tal Galili > > My Blogs: > > http://www.r-statistics.com/ > > http://www.talgalili.com > > http://www.biostatistics.co.il > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > R-help@r-project.org 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. > > > > > > -- > View this message in context: > http://www.nabble.com/Can-I-use-%22mcnemar.test%22-for-3*3-tables-%28or-is-there-a-bug-in-the-command-%29-tp24556414p24556693.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@r-project.org 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. > -- ---------------------------------------------- My contact information: Tal Galili Phone number: 972-50-3373767 FaceBook: Tal Galili My Blogs: http://www.r-statistics.com/ http://www.talgalili.com http://www.biostatistics.co.il [[alternative HTML version deleted]]
______________________________________________ R-help@r-project.org 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.
