A student uses an electronic reaction timer. In one set of tests, the signal appears after the same fixed delay each time. In another set, the signal appears after an unpredictable delay. The student records five reaction times for each set.
| Signal delay | Reaction times (s) |
|---|---|
| Fixed | 0.25, 0.23, 0.24, 0.22, 0.26 |
| Unpredictable | 0.31, 0.34, 0.29, 0.33, 0.33 |
Calculate the mean reaction time for each set of tests.
Evaluate what the results suggest about using a fixed delay instead of an unpredictable delay, and suggest one improvement to the investigation.