Study Figure 4, which shows some fieldwork data about sediment size collected at four sites along a river bed.
| Site 1 | Site 2 | Site 3 | Site 4 | |
|---|---|---|---|---|
| Pebble 1 (cm) | 12.4 | 8.5 | 4.2 | 2.1 |
| Pebble 2 (cm) | 15.1 | 7.3 | 3.8 | 1.8 |
| Pebble 3 (cm) | 11.3 | 8.9 | 4.1 | 2.0 |
| Pebble 4 (cm) | 13.6 | 8.0 | 3.9 | 1.7 |
| Mean pebble size | 13.1 | ? | 4.0 | 1.9 |
| Range in pebble size | 3.8 | 1.6 | 0.4 | 0.4 |
Calculate the mean pebble size at Site 2.
Give your answer to one decimal place.
You must show all your workings.
