Before a new contact lens solution can be sold, it must be tested on cultured human eye cells.
Cultured human eye cells were placed into four identical flasks.
Artificial tear fluid was added to each flask, and a different brand of contact lens solution was added to three of the flasks.
The human cells were left for four hours and the percentage of cells that were healthy was recorded.
| Substance added to the human eye cells | Percentage of healthy cells after 4 hours (%) |
|---|---|
| Tear fluid only | 92 |
| Contact lens solution Brand A | 91 |
| Contact lens solution Brand B | 93 |
| Contact lens solution Brand C | 91 |
Explain the conclusion that can be made from these data.
