From: P Ehlers <ehlers_at_math.ucalgary.ca>

Date: Wed 21 Dec 2005 - 10:20:52 EST

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> Well, it's open source... You could just go check.

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*> W is the sum of the ranks in the first group, minus the minimum value
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*> it can attain, namely sum(1:n1) == n1*(n1+1)/2. In the tied cases, the
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*> actual minimum could be larger.
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*>
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*> The T would seem to be asymptotically normal
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> Asymptotic Wilcoxon Mann-Whitney Rank Sum Test

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*> data: pd by groups 12-26 Weeks, At term
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*> T = -1.2247, p-value = 0.2207
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*> alternative hypothesis: true mu is not equal to 0
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> [1] 0.2206883

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*> so a good guess at its definition is that it is obtained from W or one
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*> of the others by subtracting the mean and dividing with the SD.
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*>
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R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Dec 21 10:30:15 2005

Date: Wed 21 Dec 2005 - 10:20:52 EST

Peter Dalgaard wrote:

> Bob Green <bgreen@dyson.brisnet.org.au> writes:

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>>An earlier post had posed the question: "Does anybody know what is relation >>between 'T' value calculated by 'wilcox_test' function (coin package) and >>more common 'W' value?" >> >>I found the question interesting and ran the commands in R and SPSS. The W >>reported by R did not seem to correspond to either Mann-Whitney U, >>Wilcoxon W or the Z which I have more commonly used. Correction for ties >>may have affected my results. >> >>Can anyone else explain what the reported W is and the relation to the >>reported T?

> Well, it's open source... You could just go check.

>>wilcox_test(pd ~ age, data = water_transfer,distribution="asymp")

> Asymptotic Wilcoxon Mann-Whitney Rank Sum Test

>>pnorm(-1.2247)*2

> [1] 0.2206883

With the SD adjusted for ties, of course. (See, e.g., Conover's book.)

Peter Ehlers

University of Calgary

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Dec 21 10:30:15 2005

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