Compare7 marksChallenge
A researcher investigates variation in leaf width (mm) in a species of alpine plant, Lobelia gibberosa. Two populations were sampled: Population A from a lowland valley (altitude 500 m) and Population B from a high-altitude ridge (altitude 2000 m). The summary statistics for leaf width from 30 individuals per population are shown below.
| Population | Mean leaf width (mm) | Standard deviation (mm) | Sample size (n) |
|---|---|---|---|
| A (lowland) | 12.4 | 1.8 | 30 |
| B (highland) | 10.1 | 2.1 | 30 |
An independent-samples t-test comparing the means gave a t-value of 2.45, with a p-value of 0.018 (significant at the 5% level).
Compare the two populations with respect to their variation in leaf width. In your answer, refer to:
- the type of variation (discontinuous or continuous) shown within each population;
- the likely genetic and environmental influences on this variation;
- what the t-test result indicates about the difference in mean leaf width between the populations.