is about is_proxy_for is denoted by has value normal distribution hypothesis polychotomous variable correlation coefficient continuous variable polychoric correlation coefficient true 2 2 Alejandra Gonzalez-Beltran Orlaith Burke Philippe Rocca-Serra adapted from: http://www.rasch.org/rmt/rmt193c.htm and http://en.wikipedia.org/wiki/Polychoric_correlation http://cran.r-project.org/web/packages/polycor/ polychor(x, y, ML = FALSE, control = list(), std.err = FALSE, maxcor=.9999) polychoric correlation coefficient is a correlation coefficient which is computed over 2 variables to characterise an association by proxy with 2 (latent) variables which are assumed to be continuous and normally distributed. ready for release