Name of coefficient Uses
Pearson r Both variables are interval
(height with weight)
Point biserial 1 variable interval, other
nominal (weight with gender)
Biserial 1 variable interval, the other
dichotomized interval
(height in inches with weight
recorded as either light/heavy)
Tetrachoric Both variables are dichotomized
interval (height recorded as
short/tall correlated with weight
recorded as light or heavy)
Spearman's rho Both variables are ordinal (people
ranked in terms of height and
weight)
Phi Coefficient Both variables are nominal
(Gender and race correlated)