[Scipy-tickets] [SciPy] #1744: Wilcoxon signed rank test validation on textbook example fails

SciPy Trac scipy-tickets@scipy....
Thu Oct 11 14:30:57 CDT 2012


#1744: Wilcoxon signed rank test validation on textbook example fails
-------------------------+--------------------------------------------------
 Reporter:  chris1869    |       Owner:  somebody         
     Type:  defect       |      Status:  needs_review     
 Priority:  normal       |   Milestone:  StatisticsCleanup
Component:  scipy.stats  |     Version:  0.11.0           
 Keywords:  malfunction  |  
-------------------------+--------------------------------------------------

Comment(by josefpktd):

 R gives the same test statistic as scipy, but pvalue looks strange

 {{{
 > x= c(0, 0, 0, 0, 0 , -1, -1, -1, -1, -1, +1, -2, -2, -4, +4)
 > wilcox.test(x)

         Wilcoxon signed rank test with continuity correction

 data:  x
 V = 13, p-value = 0.1436
 alternative hypothesis: true location is not equal to 0

 Warning messages:
 1: In wilcox.test.default(x) : cannot compute exact p-value with ties
 2: In wilcox.test.default(x) : cannot compute exact p-value with zeroes
 }}}

-- 
Ticket URL: <http://projects.scipy.org/scipy/ticket/1744#comment:3>
SciPy <http://www.scipy.org>
SciPy is open-source software for mathematics, science, and engineering.


More information about the Scipy-tickets mailing list