An investigation was carried out to study how continuous screen time affects the near point of vision (the closest distance at which the eye can focus clearly) in young adults.
Volunteers were asked to read text on a smartphone screen at maximum brightness. At set intervals, each volunteer moved a card with small printed text closer to their eyes until the letters first began to blur. This distance was measured and recorded.
The results are shown in Table 1.
Table 1
| Screen time (hours) | Near point of vision (cm) | Mean distance (cm) | ||
|---|---|---|---|---|
| Volunteer 1 | Volunteer 2 | Volunteer 3 | ||
| 0 | 12.4 | 12.1 | 12.7 | 12.4 |
| 2 | 18.2 | 17.9 | 18.5 | 18.2 |
| 4 | 23.4 | 24.1 | 23.8 | 23.8 |
| 6 | 28.3 | 29.5 | 28.7 | Y |
Calculate the mean distance Y for the volunteers after 6 hours of screen time.
Give your answer to three significant figures.
