chi square table

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chi square table

cruz-2
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

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Re: chi square table

David Scott-6
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

_________________________________________________________________
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  The University of Auckland, PB 92019
  Auckland 1142,    NEW ZEALAND
Phone: +64 9 373 7599 ext 86830 Fax: +64 9 373 7000
Email: [hidden email]

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Re: chi square table

Simon Blomberg-4
In reply to this post by cruz-2
> 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
>
> ______________________________________________
> [hidden email] 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.

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Re: chi square table

Erik Iverson
In reply to this post by cruz-2
 > 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
>
> ______________________________________________
> [hidden email] 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.

______________________________________________
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Re: chi square table

Berwin A Turlach
In reply to this post by cruz-2
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

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Re: chi square table

Peter Dalgaard
Berwin A Turlach wrote:


> <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>

Exposure to certain groups of students might change your opinions
there.... Some of us have been teaching to people who have trouble
calculating "21% of the number of boys" so you really don't want to
throw them further off their feet by relying on mathematical nitty-gritty.

(Actually, I don't think you see z_alpha that much. It's more like "tail
area", "P value", "Two sided P value".)

--
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  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
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