CAIE A Level Biology 9700 · Selection and evolution
A student measured the heights (cm) of two groups of tomato seedlings. Group A was grown in full sunlight, Group B in shade. The results are shown.
| Group | n | Mean height (cm) | SD |
|---|---|---|---|
| A | 20 | 15.2 | 2.3 |
| B | 20 | 11.8 | 2.1 |
The t-test formula is:
The calculated t value is 3.45. The critical value for a two-tailed test at p = 0.05 is 2.10.
Explain what this result indicates about the phenotypic variation in seedling height.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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