What is a point biserial correlation?
The point biserial correlation is a measure of association between a continuous variable and a binary variable. It is constrained to be between -1 and +1. Calculation of the point biserial correlation Assume that X is a continuous variable and Y is categorical with values 0 and 1. Compute the point biserial correlation using the formula where This is mathematically equivalent to the traditional correlation formula. The interpretation is similar. The point biserial correlation is positive when large values of X are associated with Y=1 and small values of X are associated with Y=0. Examples FB represents postural sway in the forward-backward direction and is continuous. SS represents postural sway in the side-side direction and is also continuous. AGE_GRP represents the age group (0=Young, 1=Elderly) and is binary. FB and SS show a strong positive correlation with each other and a moderate correlation with age group. Postural sway correlations. Source: http://lib.stat.cmu.edu/DASL/Datafi
