.
Properties of r:
1) It is always true that -1 r 1.
2) If there is a perfect positive linear relationship between x and y, then r = 1; if there is a perfect negative linear relationship between x and y, then r = -1.
3) If there is a positive linear trend relationship between x and y, then 0 < r < 1; if there is a negative linear trend relationship between x and y, then -1 < r < 0.
4) If there is no linear relationship between x and y, then r = 0.
We will learn how to calculate r after discussing simple linear regression.
