[R] effect sizes for Wilcoxon tests

[Claus Atzenbeck]

On Tue, 15 Nov 2005, Peter Dalgaard wrote:

> > > However, for Wilcoxon tests, the formula for effect sizes is:
> > > r = Z / sqrt(N)
> > >
> > > I wonder how I can calculate the Z-score in R for a Wilcoxon test.
> >
> > Does anyone know how to calculate effect sizes for Wilcoxon tests as
> > SPSS can do? I wonder if it would be very difficult to do so with R.
>
> If the above formula is correct, it can't be hard. What I wonder is
> whether (and if so, how) it makes sense. (& the fact that SPSS does it
> is no guarantee...)

According to my references, the formula is OK.

However, how do I get Z from a Wilcoxon test in R?

(BTW, I have to correct myself: SPSS delivers Z. The effect size was
calculated by the author of one of my books using the above mentioned
formula.)

Claus