phi2poly {psych}R Documentation

Convert a phi coefficient to a polychoric correlation

Description

Given a phi coefficient (a Pearson r calculated on two dichotomous variables), and the marginal frequencies (in percentages), what is the corresponding estimate of the polychoric correlation?

Given a two x two table of counts

a b
c d

The phi coefficient is (a - (a+b)*(a+c))/sqrt((a+b)(a+c)(b+d)(c+c)).

This function reproduces the cell entries for specified marginals and then calls John Fox's polychor function.

Usage

phi2poly(ph, cp, cc)

Arguments

ph

phi

cp

probability of the predictor – the so called selection ratio

cc

probability of the criterion – the so called success rate.

Details

requires the mvtnorm package

Value

a polychoric correlation

Author(s)

William Revelle

See Also

tetrachoric, polychor.matrix, Yule2phi.matrix, phi2poly.matrix

Examples

#phi2poly(.3,.5,.5)
#phi2poly(.3,.3,.7)

[Package psych version 1.2.1 Index]