ES.w2() - what is the name of the statistic?

[FlorinAndrei]

I'm looking at the documentation and the source code for ES.w2(). The way the statistic is calculated is quite clear. It is not clear what is the name of that statistic. All I see is a reference to Cohen's 1988 book, which I do not have yet.

So what is it called? It's not Cohen's Phi, or V, is it?

[volcic]

According to Cohen (1988, p. 216), the effect size indices calculated with ES.w1() and ES.w2() are simply called w. If needed, w can be transformed into other measures of association (e.g., Pearson's coefficient of contingency (C), the fourfold point correlation coefficient for 2x2 tables ($\phi$), or Cramer's $\phi$' for contingency tables of any dimensionality). Note: the symbol $\phi$ here should not be confused with the arcsine transformation of proportions used in calculating power for differences between proportions.