When you typed x as a command, R runs the command print(x). That function produces a summary of the results which may include round off numbers to a few decimal places to make them more readable. When you typed x$statistic, you got the unrounded version of the result 5.6e-31 which I think you will agree is pretty close to 0.
---------------------------------------------- David L Carlson Associate Professor of Anthropology Texas A&M University College Station, TX 77843-4352 > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of Troy S > Sent: Monday, December 03, 2012 3:41 PM > To: r-help@r-project.org > Subject: [R] Chi-squared test when observed near expected > > Dear UseRs, > > I'm running a chi-squared test where the expected matrix is the same as > the > observed, after rounding. R reports a X-squared of zero with a p value > of > one. I can justify this because any other result will deviate at least > as > much from the expected because what we observe is the expected, after > rounding. But the formula for X-squared, sum (O-E)^2/E gives a > positive > value. What is the reason for X-Squared being zero in this case? > > Troy > > > trial<-as.table(matrix(c(26,16,13,7),ncol=2)) > > x<-chisq.test(trial) > > x > > > > data: trial > X-squared = 0, df = 1, p-value = 1 > > > x$expected > A B > A 26.41935 12.580645 > B 15.58065 7.419355 > > > > x$statistic > X-squared > 5.596653e-31 > > (x$observed-x$expected)^2/x$expected > A B > A 0.006656426 0.013978495 > B 0.011286983 0.023702665 > > sum((x$observed-x$expected)^2/x$expected) > [1] 0.05562457 > > > > [[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. ______________________________________________ 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.
