[Scipy-tickets] [SciPy] #1401: Negative p from fisher_exact

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Wed Mar 2 17:47:47 CST 2011


#1401: Negative p from fisher_exact
--------------------------+-------------------------------------------------
 Reporter:  fubar         |       Owner:  somebody
     Type:  defect        |      Status:  new     
 Priority:  normal        |   Milestone:          
Component:  scipy.stats   |     Version:  0.9.0   
 Keywords:  fisher_exact  |  
--------------------------+-------------------------------------------------

Comment(by fubar):

 In case this helps, R gives:

 {{{
 > fisher.test(matrix(c(17704,496,1065,77),nrow=2))

         Fisher's Exact Test for Count Data

 data:  matrix(c(17704, 496, 1065, 77), nrow = 2)
 p-value = 1.363e-11
 alternative hypothesis: true odds ratio is not equal to 1
 95 percent confidence interval:
  1.986867 3.314936
 sample estimates:
 odds ratio
   2.580437

 > fisher.test(matrix(c(17704,496,1065,76),nrow=2))

         Fisher's Exact Test for Count Data

 data:  matrix(c(17704, 496, 1065, 76), nrow = 2)
 p-value = 2.666e-11
 alternative hypothesis: true odds ratio is not equal to 1
 95 percent confidence interval:
  1.957972 3.276038
 sample estimates:
 odds ratio
   2.546942

 > fisher.test(matrix(c(17704,496,1065,75),nrow=2))

         Fisher's Exact Test for Count Data

 data:  matrix(c(17704, 496, 1065, 75), nrow = 2)
 p-value = 5.56e-11
 alternative hypothesis: true odds ratio is not equal to 1
 95 percent confidence interval:
  1.929286 3.237378
 sample estimates:
 odds ratio
   2.513442

 > sessionInfo()
 R version 2.12.0 (2010-10-15)
 Platform: x86_64-unknown-linux-gnu (64-bit)

 locale:
  [1] LC_CTYPE=en_AU.UTF-8       LC_NUMERIC=C
  [3] LC_TIME=en_AU.UTF-8        LC_COLLATE=en_AU.UTF-8
  [5] LC_MONETARY=C              LC_MESSAGES=en_AU.UTF-8
  [7] LC_PAPER=en_AU.UTF-8       LC_NAME=C
  [9] LC_ADDRESS=C               LC_TELEPHONE=C
 [11] LC_MEASUREMENT=en_AU.UTF-8 LC_IDENTIFICATION=C

 attached base packages:
 [1] stats     graphics  grDevices utils     datasets  methods   base

 loaded via a namespace (and not attached):
 [1] tools_2.12.0
 }}}

-- 
Ticket URL: <http://projects.scipy.org/scipy/ticket/1401#comment:1>
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