I have four samples (x1, x2, x3, and x4) with their values shown below:
> x1
[1] 0.6343592 0.4960767 0.5802182 0.5224468 0.5774899 0.4938405
[7] 0.6413160 0.6168486 0.4975457 0.6120071 0.5813722 0.5425456
[13] 0.4792247 0.5383875 0.5702392 0.4406344 0.5309179 0.5509874
[19] 0.5457732 0.5413252 0.5338342 0.4286551 0.4222129 0.5207673
[25] 0.4984457 0.5304531
> x2
[1] 0.7181799 0.4925333 0.5131511 0.5536727 0.6369794 0.5294548
[7] 0.5027039 0.5640035 0.5602509 0.6028623 0.5796146 0.5604145
[13] 0.5433392 0.5080444 0.5376570 0.4539623 0.5471905 0.5695738
[19] 0.5545275 0.5999702 0.5630518 0.5747470 0.5287676 0.4027051
[25] 0.4779424 0.5447307
> x3
[1] 0.5948402 0.5494434 0.5960296 0.5634001 0.6044936 0.6109550
[7] 0.5234166 0.6028709 0.5049527 0.6092599 0.6330479 0.6176069
[13] 0.5755432 0.5345823 0.5176935 0.5439285 0.5304621 0.5560827
[19] 0.6256231 0.5500233 0.5482850 0.5255282 0.5158963 0.5380739
[25] 0.5453110 0.5395740
> x4
[1] 0.6806158 0.5835167 0.6193832 0.4222333 0.5425774 0.4785489
[7] 0.4474077 0.4303011 0.6169782 0.4598568 0.4713550 0.4516266
[13] 0.4754098 0.6126220 0.4883478 0.4667159 0.4642833 0.5761202
[19] 0.4414092 0.5019286 0.5978668 0.4861931 0.4944485 0.4815222
[25] 0.4877936 0.5955430
I tried to calculate the p-value of kruskal.test, which was pretty straightforward.
> kruskal.test(list(x1, x2, x3, x4))
Kruskal-Wallis chi-squared = 9.9539, df = 3, p-value = 0.01896
However, when I tried to find out the result of kruskal.test p-value between any of these samples, the results were equal to 0.4624 for any pairs of them. Do these results have any interpretation? More clearly: am I doing something wrong to get these identical results for different samples or there are other reasons that I should know of?
> kruskal.test(x1, x2)
Kruskal-Wallis chi-squared = 25, df = 25, p-value = 0.4624
> kruskal.test(x1, x3)
Kruskal-Wallis chi-squared = 25, df = 25, p-value = 0.4624
> kruskal.test(x2, x3)
Kruskal-Wallis chi-squared = 25, df = 25, p-value = 0.4624
