Hello Charles, Thank you for the detail reply. I am still left with the leading question which is: which test should I use when analyzing the 3 by 3 matrix I have? The mcnemar.test or the mh_test? Is the one necessarily better then the other? (for example for sparser matrices ?)
What about: mh_test(as.table(matrix(1:16,4))) It returns a very significant result: chi-squared = 11.4098, df = 3, p-value = 0.009704 Where as "mcnemar.test(matrix(1:16,4))", didn't: McNemar's chi-squared = 11.5495, df = 6, p-value = 0.0728 So which one is "right" ? (from the looks of it, the mh_test is doing much better) Should the strategy be to try and use both methods, and start digging when one doesn't sit well with the other? Thanks, Tal On Sun, Jul 19, 2009 at 10:26 PM, Charles C. Berry <cbe...@tajo.ucsd.edu>wrote: > On Sun, 19 Jul 2009, Tal Galili wrote: > > 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 >> ? >> > > print(mcnemar.test) > > will show you what it does. > > Because the results for the simple example I gave are rather different (P >> value of 0.053 VS 0.73) >> > > The test mcnemar.test() constructs is one of symmetry, which is equivalent > to marginal homogenity in hierarchical log-linear models as I recall from > Bishop, Fienberg, and Holland's 1975 opus on count data. > > Stuart-Maxwell uses the dispersion matrix of marginal difference. > > These are two different tests. I suspect that Stuart-Maxwell is less > susceptible to continuity issues in very sparse tables, which may account > for the difference you see here. > > > >> 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?) >> > > Well, the code is pretty straightforward and > > mcnemar.test(matrix(1:16,4)) > > returns 11.5495 which is correct. > > It looks like there is nothing to report. 3,1,5), ncol = 3)))) > > > Chuck > > >> 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]] >> >> >> > Charles C. Berry (858) 534-2098 > Dept of Family/Preventive > Medicine > E mailto:cbe...@tajo.ucsd.edu UC San Diego > http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901 > > -- ---------------------------------------------- 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.
