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Consider the following daily returns of a portfolio for six days.
| i | X | Y |
|---|---|---|
| 1 | 0.5 | 2.5 |
| 2 | 1.3 | 6.5 |
| 3 | -0.5 | -2.3 |
| 4 | -0.6 | -5.4 |
| 5 | 4.3 | 3.0 |
| 6 | 3.1 | 2.1 |
What is the value of the rank correlation coefficient?
A
0.4562
B
0.6754
C
0.7862
D
0.7143
Explanation:
The rank correlation coefficient (Spearman's rank correlation) is calculated using the formula:
First, we need to rank the X and Y values separately:
Ranking X values (ascending order):
Ranking Y values (ascending order):
Now we calculate the squared differences between ranks:
| i | X | Y | Rₓ | Rᵧ | (Rₓ − Rᵧ)² |
|---|---|---|---|---|---|
| 1 | 0.5 | 2.5 | 4 | 3 | 1 |
| 2 | 1.3 | 6.5 | 3 | 1 | 4 |
| 3 | -0.5 | -2.3 | 5 | 5 | 0 |
| 4 | -0.6 | -5.4 | 6 | 6 | 0 |
| 5 | 4.3 | 3.0 | 1 | 2 | 1 |
| 6 | 3.1 | 2.1 | 2 | 4 | 4 |
| Sum | 10 |
Now plug into the formula:
Therefore, the rank correlation coefficient is 0.7143, which corresponds to option D.