> Hello everybody, > > I'm seeing some strange behavior on R 1.8.1 on Intel/Linux compiled > with gcc 3.2.2. The p-value calculated from the chisq.test function is > incorrect for some input values: > > > > chisq.test(matrix(c(0, 1, 1, 12555), 2, 2), simulate.p.value=TRUE) > > Pearson's Chi-squared test with simulated p-value (based on 2000 > replicates) > > data: matrix(c(0, 1, 1, 12555), 2, 2) > X-squared = 1e-04, df = NA, p-value = 1 > > > chisq.test(matrix(c(0, 1, 1, 12556), 2, 2), simulate.p.value=TRUE) > [...] > data: matrix(c(0, 1, 1, 12556), 2, 2) > X-squared = 1e-04, df = NA, p-value = < 2.2e-16 > > > chisq.test(matrix(c(0, 1, 1, 12557), 2, 2), simulate.p.value=TRUE) > [...] > data: matrix(c(0, 1, 1, 12557), 2, 2) > X-squared = 1e-04, df = NA, p-value = 1 >
this does not happen with R-1.8.1 and gcc 2.95.4 on Debian stable: R> chisq.test(matrix(c(0, 1, 1, 12555), 2, 2), simulate.p.value=TRUE)$p.value [1] 1 R> chisq.test(matrix(c(0, 1, 1, 12556), 2, 2), simulate.p.value=TRUE)$p.value [1] 1 R> chisq.test(matrix(c(0, 1, 1, 12557), 2, 2), simulate.p.value=TRUE)$p.value [1] 1 neither with R-1.9.0 (unstable). Is this reproducible without using `set.seed' on your system? Best, Torsten > > In these three calls to chisq.test, I'm varying the input matrix by > only 1 observation, but the p-value changes by 16 orders of magnitude. > This is reproducible on my system. Please let me know if any other > information would be useful. > > chisq.test works properly for these inputs on Mac OS X 10.3.1 with R > 1.8.0. I don't know if the problem is with Linux or 1.8.1. > > This bug looks very similar to bug 4718, which was reported in R 1.8.0 > and fixed in R 1.8.1. They may be related. > http://r-bugs.biostat.ku.dk/cgi-bin/R/Analyses-fixed?id=4718; > user=guest;selectid=4718 > > Jeff > > ______________________________________________ > [EMAIL PROTECTED] mailing list > https://www.stat.math.ethz.ch/mailman/listinfo/r-help > > ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
