ABSTRACT
This is a measure of how close data, representing two variables x and y, are to a straight line. Extreme values are:
(a) 0 for no correlation, i.e. either x or y formed from a set of random numbers; (b) +1 for perfect positive correlation, i.e. the variables x and y are on a perfect
straight line with positive slope; (c) −1 for perfect negative correlation and negative slope.
