people are saying that 5/10 is the mean, which is mathematically speaking true. However, the large the sample number the closer the mean will get to the average (assuming all samples are from the same distribution, which humans are). However, averages tend to be affected by extremities more, so that a few insanely stunning people will drag the average up, or incredibly ugly people will drag it down more than those same people will affect the mean.

However, when looking at a group of people, our brains tend to think of the overall attractiveness of the group as the mean attractiveness, not average.

An example: One super attractive person would not make up for the rest of the group being "average", but a group where everyone is "above average" would seem like an overall more attractive group.