From: <ripley_at_stats.ox.ac.uk>

Date: Tue 20 Dec 2005 - 16:01:03 GMT

Date: Tue 20 Dec 2005 - 16:01:03 GMT

This is the same as PR#8265, from a person also not giving his/her name
but sharing your ISP. Please don't submit a repeat, as the FAQ asks.

After last time this was raised, I checked Yates' original paper and Fisher's book and it seems that R's formula follows what they say.

Do remember that 0 is an impossible value for a chisq-distributed variable, and so one would not expect the corrected distribution to take that value with positive probability.

On Tue, 20 Dec 2005 cig69410@syd.odn.ne.jp wrote:

*> Full_Name: nobody
*

Do you expect us to take the word of `nobody' as to the correct definition of a statistic? We need your credentials and references.

> Version: 2.2.0

*> OS: any
**> Submission from: (NULL) (219.66.34.183)
**>
**>
**> 2 x 2 table, such as
**>
**>> x
**> [,1] [,2]
**> [1,] 10 12
**> [2,] 11 13
**>
**>> chisq.test(x)
**>
**> Pearson's Chi-squared test with Yates'
**> continuity correction
**>
**> data: x
**> X-squared = 0.0732, df = 1, p-value = 0.7868
**>
**> but, X-squared = 0.0732 is over corrected.
**>
**> when abs(a*d-b*c) <= sum(a,b,c,d), chisq.value must be 0!, and P-value must be
**> 1!
**>
**> code of chisq.test must be as follows
**>
**> # if (correct && nrow(x) == 2 && ncol(x) == 2) {
**> # YATES <- 0.5
**> # METHOD <- paste(METHOD, "with Yates' continuity correction")
**> # }
**> # else YATES <- 0
**> # STATISTIC <- sum((abs(x - E) - YATES)^2/E)
**> ## replace begin
**> if (correct && nrow(x) == 2 && ncol(x) == 2) {
**> STATISTIC <- if (abs(x[1,1]*x[2,2]-x[1,2]*x[2,1]) < sum(x)/2) 0
**>
**> else sum((abs(x - E) - 0.5)^2/E)
**> METHOD <- paste(METHOD, "with Yates' continuity correction")
**> }
**> else STATISTIC <- sum((abs(x - E))^2/E)
**> ## replace end
*

-- Brian D. Ripley, ripley@stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-develReceived on Wed Dec 21 03:19:53 2005

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