Sample size for biserial-phi correlation confidence interval

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.

Usage

size.ci.biphi(alpha, p1, p2, cor, w)

Arguments

alpha: alpha level for 1 - alpha confidence
p1: planning value for row 1 marginal proportion
p2: planning value for column 1 marginal proportion
cor: planning value for biserial-phi correlation
w: desired confidence interval width

Value

Returns the required sample size

Examples

size.ci.biphi(.05, .2, .5, .3, .4)
#>  Sample size
#>          195

# Should return:
#  Sample size
#          195