This test is used to measure the strength of a linear association between two variables,
where the value r = 1 means a perfect positive correlation and the value
r = -1 means a perfect negataive correlation. So, for example, you could
use this test to find out whether people's height and weight are correlated (they
will be - the taller people are, the heavier they're likely to be).

Requirements

Scale of measurement should be interval or ratio

Variables should be approximately normally distributed