Hi, How do we get the value of a chi square as we usually look up on the table on our text book? i.e. Chi-square(0.01, df=8), the text book table gives 20.090> dchisq(0.01, df=8)[1] 1.036471e-08> pchisq(0.01, df=8)[1] 2.593772e-11> qchisq(0.01, df=8)[1] 1.646497>nono of them give me 20.090 Thanks, cruz
On Fri, 7 Nov 2008, cruz wrote:> Hi, > > How do we get the value of a chi square as we usually look up on the > table on our text book? > > i.e. Chi-square(0.01, df=8), the text book table gives 20.090 > >> dchisq(0.01, df=8) > [1] 1.036471e-08 >> pchisq(0.01, df=8) > [1] 2.593772e-11 >> qchisq(0.01, df=8) > [1] 1.646497 >> > > nono of them give me 20.090 > > Thanks, > cruz >> qchisq(0.99, df=8)[1] 20.09024 _________________________________________________________________ David Scott Department of Statistics, Tamaki Campus The University of Auckland, PB 92019 Auckland 1142, NEW ZEALAND Phone: +64 9 373 7599 ext 86830 Fax: +64 9 373 7000 Email: d.scott at auckland.ac.nz Graduate Officer, Department of Statistics Director of Consulting, Department of Statistics
> qchisq(0.01, df=8, lower.tail=FALSE)[1] 20.09024>See ?dchisq On Fri, 2008-11-07 at 09:47 +0800, cruz wrote:> Hi, > > How do we get the value of a chi square as we usually look up on the > table on our text book? > > i.e. Chi-square(0.01, df=8), the text book table gives 20.090 > > > dchisq(0.01, df=8) > [1] 1.036471e-08 > > pchisq(0.01, df=8) > [1] 2.593772e-11 > > qchisq(0.01, df=8) > [1] 1.646497 > > > > nono of them give me 20.090 > > Thanks, > cruz > > ______________________________________________ > R-help at 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.-- Simon Blomberg, BSc (Hons), PhD, MAppStat. Lecturer and Consultant Statistician Faculty of Biological and Chemical Sciences The University of Queensland St. Lucia Queensland 4072 Australia Room 320 Goddard Building (8) T: +61 7 3365 2506 http://www.uq.edu.au/~uqsblomb email: S.Blomberg1_at_uq.edu.au Policies: 1. I will NOT analyse your data for you. 2. Your deadline is your problem. The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data. - John Tukey.
> qchisq(0.01, df = 8, lower.tail = FALSE)[1] 20.09024 cruz wrote:> Hi, > > How do we get the value of a chi square as we usually look up on the > table on our text book? > > i.e. Chi-square(0.01, df=8), the text book table gives 20.090 > >> dchisq(0.01, df=8) > [1] 1.036471e-08 >> pchisq(0.01, df=8) > [1] 2.593772e-11 >> qchisq(0.01, df=8) > [1] 1.646497 > > nono of them give me 20.090 > > Thanks, > cruz > > ______________________________________________ > R-help at 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.
G'day Cruz, On Fri, 7 Nov 2008 09:47:47 +0800 cruz <cruadam at gmail.com> wrote:> Hi, > > How do we get the value of a chi square as we usually look up on the > table on our text book? > > i.e. Chi-square(0.01, df=8), the text book table gives 20.090 > > > dchisq(0.01, df=8) > [1] 1.036471e-08 > > pchisq(0.01, df=8) > [1] 2.593772e-11 > > qchisq(0.01, df=8) > [1] 1.646497 > > > > nono of them give me 20.090The value that your textbook denotes, presumably, with chi^2_0.01 (or some similar notatation) is in fact the 0.99 quantile of the chi-square distribution; which R readily calculates: R> qchisq(0.99, df=8) [1] 20.09024 <rant on> That's the problem with introductory textbook whose author think they do the students a favour by using notation as z_alpha, z_0.01, z_(alpha/2) instead of z_(1-alpha), z_0.99, z_(1-alpha/2), respectively. In my opinion this produces in the long run only more confusion and does not help students at all. It just panders to intellectual laziness of (some) students and shows a great deal of confusion on the side of the authors. I would search another textbook <rand off> Cheers, Berwin =========================== Full address ============================Berwin A Turlach Tel.: +65 6516 4416 (secr) Dept of Statistics and Applied Probability +65 6516 6650 (self) Faculty of Science FAX : +65 6872 3919 National University of Singapore 6 Science Drive 2, Blk S16, Level 7 e-mail: statba at nus.edu.sg Singapore 117546 http://www.stat.nus.edu.sg/~statba