From p.dalgaard at biostat.ku.dk  Fri May 12 16:48:23 2006
From: p.dalgaard at biostat.ku.dk (Peter Dalgaard)
Date: 12 May 2006 16:48:23 +0200
Subject: [Rd] wilcox.exact function (PR#8856)
In-Reply-To: <20060512143242.B2770E93A@slim.kubism.ku.dk>
References: <20060512143242.B2770E93A@slim.kubism.ku.dk>
Message-ID: <x2zmhn5mfc.fsf@turmalin.kubism.ku.dk>

pat.hodgson at sympatico.ca writes:

> Full_Name: Patrick Hodgson
> Version: 2.0
> OS: solaris 2.9
> Submission from: (NULL) (65.94.128.161)
> 
> 
> The value reported for the parameter W in the function wilcox.exact appears to
> be incorrect.  I have checked the reference in the help file for this function
> (Myles & Hollander 1973, as well as 2nd ed. 1999 by same authors) and it is
> clear that W is the sum of the ranks of the data set with the smaller number of
> members.

You should not use the bug repository to report on a (non-core)
package. However, it is the same W used by wilcox.test and
help(wilcox.test)  has the explanation. 



> Here is sample input/output:
> > x<-c(1,2,3,4,5,6,7,8,9,10)
> > y<-c(11,12,13,14,15)           
> > library(exactRankTests)
> > wil<-wilcox.exact(x,y)
> > wil
> 
>         Exact Wilcoxon rank sum test
> 
> data:  x and y 
> W = 0, p-value = 0.000666
> alternative hypothesis: true mu is not equal to 0 
> 
> In this case W should be the sum of the ranks of y (coincidentally also the
> values of the y data)= 11+12+13+14+15 = 65.
> W of zero is ridiculous.
> 
> Similarly, in this case W should be 2+4+6+8 = 20, not 10 as reported.
> > x<-c(1,3,5,7,9)
> > y<-c(2,4,6,8)
> > wil<-wilcox.exact(x,y)
> > wil
> 
>         Exact Wilcoxon rank sum test
> 
> data:  x and y 
> W = 10, p-value = 1
> alternative hypothesis: true mu is not equal to 0
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
> 

-- 
   O__  ---- Peter Dalgaard             ?ster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)                  FAX: (+45) 35327907



[Rd] wilcox.exact function (PR#8856)
Peter Dalgaard