An agricultural scientist investigated whether the light spectrum of LED grow lights affects the yield of tomato plants. Two groups of seven tomato plants were grown for 12 weeks. Group 1 was grown under a Red-dominant spectrum, while Group 2 was grown under a Blue-dominant spectrum. The number of fully ripened tomatoes harvested from each plant is shown in the table below.
| Number of ripened tomatoes | |||||
|---|---|---|---|---|---|
| Red LED group | Blue LED group | ||||
| Plant | Yield | Rank | Plant | Yield | Rank |
| a | 15 | 4 | a | 10 | 1 |
| b | 18 | 5.5 | b | 12 | 2 |
| c | 19 | 7 | c | 14 | 3 |
| d | 21 | 9 | d | 18 | 5.5 |
| e | 22 | 10 | e | 20 | 8 |
| f | 25 | 12 | f | 23 | 11 |
| g | 26 | 13 | g | 27 | 14 |
| n1=7n_1 = 7n1=7 | n2=7n_2 = 7n2=7 |
Before conducting a Mann-Whitney U test to compare the yields, the data from both groups must be pooled and ranked. In the results, two plants have the same yield of 18. Explain how this is dealt with when ranking the data.
513 exam-style questions on OCR A Level Psychology Data recording, analysis and presentation. Each one has a worked solution and a mark scheme showing where the marks go.