Prof Brian Ripley wrote:
> On Sun, 30 Oct 2005, P Ehlers wrote: > >> [EMAIL PROTECTED] wrote: >> >>> Full_Name: foo ba baz >>> Version: R2.2.0 >>> OS: Mac OS X (10.4) >>> Submission from: (NULL) (219.66.32.183) >>> >>> >>> chisq.test(matrix(c(9,10,9,11),2,2)) >>> >>> Chi-square value must be 0, and, P value must be 0 >>> R does over correction >>> >>> when | a d - b c | < n / 2 ，chi-sq must be 0 >> >> >> (Presumably, you mean P-value = 1.) >> If you don't want the correction, set correct=FALSE. (The >> results won't differ much.) >> >> A better example is >> >> chisq.test(matrix(c(9,10,9,10),2,2)) >> >> for which R probably should return X-squared = 0. > > > R is using the correction that almost all the sources I looked at > suggest. You can't go around adjusting X^2 for just some values of the > data: the claim is that the adjusted statistic has a more accurate chisq > distribution under the null. > > I think at this remove it does not matter what Yates' suggested > (although if I were writing a textbook I would find out), especially as > the R documentation does not mention Yates. > You're quite right that, for consistency, the correction should be applied even in the silly example I gave. And, of course, one should not be doing a chisquare test on silly examples. Peter Ehlers ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
