This repository was archived by the owner on Nov 19, 2020. It is now read-only.
This repository was archived by the owner on Nov 19, 2020. It is now read-only.
Mann-Whitney-U Test producing strange results #857
Description
Dear @cesarsouza
I just found out, that the MannWhitneyWilcoxonTest class may be buggy.
Given the following sample vector, when I pass it in as sample one and sample two vector, the Accord.NET implementation shows a p-Value of 0.41 or the like.
According to R, for the given vector, the p-Value should be 1 (exactly).
a <- c(250,200,450,400,250,250,350,0,200,400,300,600,200,200,
550,100,300,250,350,200,550,200,450,400,200,400,450,
200,400,400,500,450,300,250,200)
b <- c(250,200,450,400,250,250,350,0,200,400,300,600,200,200,
550,100,300,250,350,200,550,200,450,400,200,400,450,
200,400,400,500,450,300,250,200)
wilcox.test(a, b)Gives the following output:
Wilcoxon rank sum test with continuity correction
data: a and b
W = 612.5, p-value = 1
alternative hypothesis: true location shift is not equal to 0
Warning message:
In wilcox.test.default(a, b) : cannot compute exact p-value with tiesI have other sample vectors, which show the same behavior. R always shows p-Value of 1 for them.
Thanks in advance,
Harald