G'day Cruz,

On Fri, 7 Nov 2008 09:47:47 +0800

cruz <

[hidden email]> 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

6 Science Drive 2, Blk S16, Level 7 e-mail:

[hidden email]
Singapore 117546

http://www.stat.nus.edu.sg/~statba______________________________________________

[hidden email] mailing list

https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide

http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.