size.ci.biphi: Sample size for biserial-phi correlation confidence interval
Description
Computes the sample size required to estimate a biserial-phi correlation
with desired confidence interval precision. Set the biserial-phi planning
value to the smallest absolute value within a plausible range for a
conservatively large sample size. The column variable is assumed to be
naturally dichotomous and the row variable is assumed to be artificially
dichotomous.