CTT (version 2.3.3)

polyserial: Function for calculating polyserial correlations

Description

This function calculates polyserial correlations using either an ad hoc or ML estimator.

Usage

polyserial(x, y, ml = TRUE)

Arguments

x

A continuous variable.

y

An ordinal variable with at least two categories.

ml

A logical variable indicating whether to use a formal maximum likelihood estimator (default) or an ad hoc estimator.

Value

Returns the polyserial correlation.

Details

The variables should be numeric. The function returns NA is y has only one category.

References

Olsson, U., Drasgow, F. & Dorans, N. J. (1982). The Polyserial Correlation Coefficient. Psychometika, 47, 337-347.

Examples

# NOT RUN {
x <- rnorm(500, 50,5)
y <- x + rnorm(500,0,2)
x <- x + rnorm(500,0,2)
cor(x,y)

y <- ifelse(y>50,1,0)

cor(x,y)

polyserial(x,y, ml=FALSE)
polyserial(x,y)
# }