The warning means that you have many cells with expected values less than 5 (4 of 8 cells in this case) so that the chi square estimate may be inflated. The good news is that the probability of the inflated chi square is .0978 which you probably would not consider to be significant anyway. If you want to get a simulated p value using Monte Carlo simulation (see the references in the manual page for chisq.test), just change the call to
chisq.test(tabele, simulate.p.value=TRUE, B=2000) When I run this five times, I get probability estimates ranging from .09795 to .1089. Alternatively, get more data. ---------------------------------------------- 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 Omphalodes Verna > Sent: Tuesday, June 26, 2012 1:28 PM > To: r-help@r-project.org > Subject: [R] chisq.test > > Dear list! > > I would like to calculate "chisq.test" on simple data set with 70 > observations, but the output is ''Warning message:'' > > Warning message: > In chisq.test(tabele) : Chi-squared approximation may be incorrect > > > Here is an example: > > tabele <- matrix(c(11, 3, 3, 18, 3, 6, 5, 21), ncol = 4, byrow > = TRUE) > dimnames(tabela) <- list( > "SEX" = c("M","F"), > "HAIR" = c("Brown", "Black", "Red", "Blonde")) > addmargins(tabele) > prop.table(tabele) > chisq.test(tabele) > Please, give me an advice / suggestion / recommendation. > > Thanks a lot to all, OV > > [[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.