d2S function

Covert Cohen's d to |S|

Converts Cohen's d robust effect size index (S) using the formula from Vandekar, Tao, & Blume (2020).

d2S(d, pi = 0.5)

Arguments

• d: Numeric, value of Cohen's d.
• pi: Numeric, the sampling proportions.

Returns

Returns an estimate the robust effect size index

Details

The pi parameter comes from the fact that Cohen's d doesn't account for unequal sample proportions in the population, but S does.

The default is set to a natural value 1/2, which corresponds to a case control design, for example, where sampling proportions always are controlled by the experimenter.

The formula to convert Cohen's d to S is:

$S = d/\sqrt( 1/\pi + 1/ (1 - \pi))$

Examples

# Consider an experiment with equal sampling proportions and a medium effect size
# corresponding to a Cohen's d of 0.5.
# convert to RESI (S)
d2S(d = 0.5)

# This corresponds to a RESI of 0.25.