4. For a project a student collects data on engine size and sales over a period of time for the models of cars made by one particular manufacturer. Her results are shown in the table below.
| 1.1 | 1.3 | 1.6 | 2.1 | 2.4 | 2.6 | 2.8 | 3.0 |
| Sales | 527 | 632 | 840 | 619 | 350 | 425 | 487 | 401 |
- Calculate Spearman's rank correlation coefficient for these data.
- Stating your hypotheses clearly, test at the \(5 \%\) level of significance whether or not there is any evidence of correlation.
- Explain why it is more appropriate to use Spearman's rank correlation coefficient for this test than the product moment correlation coefficient.
(2 marks)