1. The study group was dichotomized by the age of 75 years at RC.

2. Biserial r rb Both variables are continuous but one has been arbitrarily dichotomized Score on employment test (continuous) with rating of "satisfactory" or "unsatisfactory" in terms of numbers of errors made on job (arbitrary dichotomy) Point Biserial r rpb Correlation between one continuous variable and a variable that is a true dichotomy