[R] Problem to interpret wilcox.test
Peter Dalgaard BSA
p.dalgaard at biostat.ku.dk
Thu Dec 13 16:01:36 CET 2001
Emmanuel POIZOT <poizot at intechmer.cnam.fr> writes:
> I've got two set of data :
> 22.45 21.56 20.48 19.59 21.52 = A
> and
> 22.15 21.98 20.42 20.58 19.61 = B
> I perform a wilcox.test on this two set
> wilcox.test(A, B) and I'd this answer:
>
> Wilcoxon rank sum test
>
> data: A and B
> W = 12, p-value = 1
> alternative hypothesis: true mu is not equal to 0
>
> Should I interpret that there is no difference between the two sets ?
In a word, yes. No *detectable* difference that is. What the p-value
is saying is that there is no way of getting a W closer to the value
expected under the hypothesis of no difference (which is 12.5 in this
case).
--
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
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