[R] V-value in the wilcox.test resp. wilcox.exact
Peter Dalgaard BSA
p.dalgaard at biostat.ku.dk
Tue Oct 15 14:13:26 CEST 2002
Jan Malte Wiener <jan.wiener at tuebingen.mpg.de> writes:
> the way i understand the wilcox.test (or wilcox.exact) the V-value
> represents the summed up ranks of either the positive or negative
> differences, whichever sum is BIGGER.
>
> to actually look up the p-value in a table (and to quote it in a
> publication) i need the T value, which to my understanding is the
> summed up ranks of either the positive or negative differences,
> whichever sum is SMALLER.
>
> so i guess my question is: how do i get the T-value
At least for wilcox.test, V is the sum of the *positive* ranks. The
sum of the negative ranks can be obtained by switching the sign on x
and mu.
In the absence of ties and exact zeros, the two rank sums add up to
sum(1:N) == N*(N+1)/2
If ties are present, standard tables are wrong anyway...
--
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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