Product Moment Coefficient (r)
This gives an indication of the strength of the linear relationship among two variables.
Note that this formula can be rearranged to have different outlooks however the resultant is always the similar.
Illustration
Given data was observed and it is required to establish if there exists a relationship among the two.
X
15
24
25
30
35
40
45
65
70
75
Y
60
50
42
46
28
20
22
Solution
Calculate the product moment coefficient of correlation r:
Hence the correlation coefficient indicates a strong negative linear association among the two variables.