A marine biologist is investigating the relationship between the depth DDD (in metres) of a coral reef and the condition score S S\,S of the coral (ranked from 1 to 7, where 7 is the most degraded and 1 is the most pristine). She suspects that coral located at greater depths is more prone to degradation. She collects data from 7 different sites, as shown in the table below:
| Depth DDD (m) | 4.5 | 12.8 | 8.2 | 22.1 | 2.3 | 35.6 | 17.4 |
| Condition Rank SSS | 3 | 4 | 2 | 7 | 1 | 6 | 5 |
Calculate Spearman's rank correlation coefficient (rsr_srs) for these data.
Stating your hypotheses clearly and using a one-tailed test at the 5% level of significance, interpret your coefficient. (The critical value for n=7n=7n=7 at the 5% level is 0.7143).
State a reason why Spearman's rank correlation coefficient might be more appropriate than the product moment correlation coefficient (PMCC) for this specific dataset.
178 exam-style questions on WJEC A Level Maths 4.3.1 Statistical hypothesis testing (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.