An agricultural researcher investigated whether using an organic seaweed-based compost additive improves the yield of tomato plants. A sample of 18 pairs of tomato plants (each pair matched for initial height and soil condition) was used. In each pair, one plant was treated with the seaweed-based additive and the other with a standard liquid fertiliser. After 12 weeks, the difference in total fruit yield (in kg) between the two plants in each pair was recorded. The researcher categorised the results as shown in Table 1 below.
| Seaweed additive yielded more | Standard fertiliser yielded more | Yields were identical | |
|---|---|---|---|
| Number of pairs | 13 | 3 | 2 |
Explain two reasons why it was appropriate to use the sign test to analyse the results of this study. Refer to the details of the study in your answer.
121 exam-style questions on AQA A Level Psychology Inferential testing (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.