On Dec 11, 2007 12:21 PM, Patricia Garcia <
patricia.garcia.gonzalez@gmail.com> wrote:

> Hi
> I'm trying to use a Mann-Whitney test in a PCR data, like this:
>
>
> # Case the samples are similar:
> x1 <- c(19.0370805,17.51822,18.524912)
> y1 <- c(20.541484,22.039175,20.542968)
> w1 <- wilcox.test(x1,y1, paired = FALSE, alternative = c("two.sided"))
>
>
>        Wilcoxon rank sum test
>

>
> I obtain the same result: pvalue > 0.05, so i don't reject the null
> hypothesis, that both samples came from the same distribution.
> If i test other numbers the result is the same always.
>

The wilcoxon rank sum test is just that.  The sum of ranks is the same for
the different groups for both of your examples, so the value of the test
statistic and the p-value will also be the same.

Sean

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