2 A botanist believes that some species of plants produce more flowers at high altitudes than at low altitudes. In order to investigate this belief the botanist randomly samples 11 species of plants each of which occurs at both altitudes. The numbers of flowers on the plants are shown in the table.
| Species | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 |
| Number of flowers at low altitude | 5 | 3 | 4 | 7 | 2 | 9 | 6 | 5 | 4 | 11 | 2 |
| Number of flowers at high altitude | 1 | 6 | 10 | 8 | 14 | 16 | 20 | 21 | 15 | 2 | 12 |
- Use the Wilcoxon signed rank test at the 5\% significance level to test the botanist's belief.
- Explain why the Wilcoxon rank sum test should not be used for this test.