On a biology field trip, some students are studying the distribution of bluebells in an area of mixed woodland.
Three tree species dominate the woodland: beech, pine, and birch.
The students choose one beech tree, one pine tree, and one birch tree and count every individual bluebell plant within a 2 m radius of each tree.
The results are shown in the table:
| Tree Species | Bluebell population (total within 2 m radius) |
|---|---|
| Beech | 50 |
| Pine | 38 |
| Birch | 92 |
The null frequency hypothesis of the students' investigation is that the species of tree does not affect the number of bluebells growing near it.
Calculate the χ2 \chi^2\,χ2 value for the students' data using the equation:
χ2=∑(O−E)2E \chi^2 = \sum \frac{(O - E)^2}{E} χ2=∑E(O−E)2The critical value for χ2 \chi^2\,χ2 in this investigation at p=0.05p = 0.05p=0.05 is 5.991. Discuss what can be concluded from this comparison.
45 exam-style questions on OCR A A Level Biology Analysis. Each one has a worked solution and a mark scheme showing where the marks go.