In: Math
Here is a bivariate data set.
| x | y | 
|---|---|
| 50.4 | 96.8 | 
| 53.7 | 27.6 | 
| -17.6 | 158.6 | 
| 49.9 | -48.1 | 
| 30.5 | -6.1 | 
| 36.7 | 179 | 
| 43.5 | -3.9 | 
| 40.5 | 65.1 | 
| 52.1 | -129.7 | 
| 43.5 | 85.1 | 
| 33.4 | -41.4 | 
| 63.4 | -50 | 
| 25.3 | 31.8 | 
| 41.2 | 11.8 | 
| 34.4 | 149.4 | 
| 50.5 | -50.5 | 
Find the correlation coefficient and report it accurate to three
decimal places.
r =
Solution:
Correlation coefficient = r = [n∑xy - ∑x∑y]/sqrt[(n∑x^2 – (∑x)^2)*(n∑y^2 – (∑y)^2)]
The calculation table is given as below:
| 
 No.  | 
 x  | 
 y  | 
 x^2  | 
 y^2  | 
 xy  | 
| 
 1  | 
 50.4  | 
 96.8  | 
 2540.16  | 
 9370.24  | 
 4878.72  | 
| 
 2  | 
 53.7  | 
 27.6  | 
 2883.69  | 
 761.76  | 
 1482.12  | 
| 
 3  | 
 -17.6  | 
 158.6  | 
 309.76  | 
 25153.96  | 
 -2791.36  | 
| 
 4  | 
 49.9  | 
 -48.1  | 
 2490.01  | 
 2313.61  | 
 -2400.19  | 
| 
 5  | 
 30.5  | 
 -6.1  | 
 930.25  | 
 37.21  | 
 -186.05  | 
| 
 6  | 
 36.7  | 
 179  | 
 1346.89  | 
 32041  | 
 6569.3  | 
| 
 7  | 
 43.5  | 
 -3.9  | 
 1892.25  | 
 15.21  | 
 -169.65  | 
| 
 8  | 
 40.5  | 
 65.1  | 
 1640.25  | 
 4238.01  | 
 2636.55  | 
| 
 9  | 
 52.1  | 
 -129.7  | 
 2714.41  | 
 16822.09  | 
 -6757.37  | 
| 
 10  | 
 43.5  | 
 85.1  | 
 1892.25  | 
 7242.01  | 
 3701.85  | 
| 
 11  | 
 33.4  | 
 -41.4  | 
 1115.56  | 
 1713.96  | 
 -1382.76  | 
| 
 12  | 
 63.4  | 
 -50  | 
 4019.56  | 
 2500  | 
 -3170  | 
| 
 13  | 
 25.3  | 
 31.8  | 
 640.09  | 
 1011.24  | 
 804.54  | 
| 
 14  | 
 41.2  | 
 11.8  | 
 1697.44  | 
 139.24  | 
 486.16  | 
| 
 15  | 
 34.4  | 
 149.4  | 
 1183.36  | 
 22320.36  | 
 5139.36  | 
| 
 16  | 
 50.5  | 
 -50.5  | 
 2550.25  | 
 2550.25  | 
 -2550.25  | 
| 
 Total  | 
 631.4  | 
 475.5  | 
 29846.18  | 
 128230.2  | 
 6290.97  | 
From above table, we have
n = 16
∑x = 631.4
∑y = 475.5
∑x^2 = 29846.18
∑y^2 = 128230.2
∑xy = 6290.97
Correlation coefficient = r = [n∑xy - ∑x∑y]/sqrt[(n∑x^2 – (∑x)^2)*(n∑y^2 – (∑y)^2)]
Correlation coefficient = r = [16*6290.97 - 631.4*475.5]/sqrt[(16*29846.18 – 631.4^2)*(16*128230.2– 475.5^2)]
Correlation coefficient = r = -0.52595
r = -0.526