An agricultural scientist is investigating whether a new organic soil conditioner increases the crop yield of tomato plants. She records the weekly yield (in kg) of 6 test plots before and after applying the soil conditioner, and uses a Wilcoxon Signed-Ranks test to analyze the data.
| Plot | Yield before conditioner (kg) | Yield after conditioner (kg) | Difference | Rank of difference |
|---|---|---|---|---|
| A | 4.2 | 5.5 | +1.3 | 4 |
| B | 3.8 | 3.5 | -0.3 | 1 |
| C | 5.0 | 6.1 | +1.1 | 3 |
| D | 4.5 | 6.2 | +1.7 | 6 |
| E | 3.9 | 5.4 | +1.5 | 5 |
| F | 4.1 | 4.9 | +0.8 | 2 |
Explain how the calculated test statistic, TTT, is used in conjunction with the critical value to determine whether the organic soil conditioner has caused a statistically significant increase in yield.
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.