From: Berwin A Turlach <berwin_at_maths.uwa.edu.au>

Date: Fri, 07 Nov 2008 10:16:28 +0800

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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. Received on Fri 07 Nov 2008 - 02:21:24 GMT

Date: Fri, 07 Nov 2008 10:16:28 +0800

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 20.090
*

The 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
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