Marc Schwartz <marc_schwa...@me.com> [Wed, Dec 29, 2010 at 03:28:56PM CET]: > > On Dec 29, 2010, at 6:48 AM, Manoj Aravind wrote: > > > Thank you Marc :) > > It Certainly helped me to get the exact value of P. > > How to understand when to apply mcnemar.exact or just mcnemar.test? [...] >
> Generally speaking, exact tests are used for "small-ish" sample sizes. Frequently when n <100 and in many cases, much lower (eg. <50 or <30). The methods tend to become computationally impractical on "larger" data sets. Sorry for chiming in again here, but binomial tests are computationally cheap: > system.time(binom.test(48000, 100000)) User System verstrichen 0.072 0.000 0.077 You are certainly correct on Fisher's Exact Test with larger tables or Wilcoxon's Signed Rank test. [...] > One exception to the above comment, is the use of Fisher's Exact Test (FET), > which is typically advocated by folks as an alternative to a chi-square test > when **expected** cell counts are <5. However, much has been written in > recent times relative to just how conservative the FET is. One resource is: > > http://www.iancampbell.co.uk/twobytwo/twobytwo.htm > That's only because people shy away from the randomized version :-) -- Johannes Hüsing There is something fascinating about science. One gets such wholesale returns of conjecture mailto:johan...@huesing.name from such a trifling investment of fact. http://derwisch.wikidot.com (Mark Twain, "Life on the Mississippi") ______________________________________________ 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.