An investigator measured the pupil diameter of three volunteers when exposed to different light intensities.
Table 1 shows the results.
| Light intensity (lux) | Pupil diameter (mm) | Mean pupil diameter (mm) | ||
|---|---|---|---|---|
| Volunteer 1 | Volunteer 2 | Volunteer 3 | ||
| 0.5 | 7.8 | 8.2 | 8.0 | 8.0 |
| 5 | 6.1 | 5.9 | 6.0 | 6.0 |
| 50 | 4.2 | 3.8 | 4.0 | 4.0 |
| 500 | 2.6 | 2.4 | 2.5 | 2.5 |
State one conclusion that can be made from the data in Table 1.
