Some geography students have been conducting physical geography fieldwork on a pebble beach. They were investigating how sediment size changes along a beach profile. Some of their results are shown in the table below.
| Profile Site | Distance from shoreline | Pebble 1 length | Pebble 2 length | Pebble 3 length |
|---|---|---|---|---|
| 1 | 5m | 62 | 45 | 55 |
| 2 | 10m | 48 | 32 | 38 |
| 3 | 15m | 30 | 25 | 28 |
| 4 | 20m | 14 | 11 | 9 |
Suggest one problem with the recording of this data.