A nursery tests three treatments on equal groups of cuttings from the same plant variety. Conditions are otherwise identical.
Table
| Treatment | Number of cuttings | Number forming roots |
|---|---|---|
| No powder | 40 | 12 |
| Carrier powder only | 40 | 14 |
| Carrier powder with auxin | 40 | 30 |
Which comparison gives the strongest evidence for an effect of auxin?
compare 30 with 12 because the carrier is present in both
compare 30 with 14 because the carrier is present in both
compare 30 with 40 because auxin is absent from both groups
compare 14 with 12 because auxin is present in one group
46 exam-style questions on Edexcel GCSE Biology 6.3 Plant hormones, covering 6.3.1 Plant hormones and tropisms and 6.3.2 Commercial uses of plant hormones. Each one has a worked solution and a mark scheme showing where the marks go.