A student investigated how light levels affect the growth of English ivy (Hedera helix) leaves. They measured the surface area of five leaves from a deeply shaded woodland (Area X) and five leaves from a sunny south-facing wall (Area Y).
Their results are shown in the table below:
| Ivy leaf sample | Leaf surface area (cm2\text{cm}^2cm2) | |
|---|---|---|
| Area X (Deep shade) | Area Y (Sunny wall) | |
| 1 | 34 | 19 |
| 2 | 36 | 17 |
| 3 | 33 | 18 |
| 4 | (15) | 20 |
| 5 | 37 | 18 |
| Mean | 35 | 18 |
(Note: The value in brackets is an anomalous result and was not used to calculate the mean for Area X).
Explain the difference in the mean leaf surface area of the ivy leaves in the deep shade (Area X) compared to those in the sunlight (Area Y).
