Question

Here are 10 test scores: 30, 74, 76, 77, 78, 79, 80, 80, 82, 84. The mean of these scores is 74.

Does this set have an outlier and, if so, how does removing it affect the mean?

Answer 1

The outlier is 30 (yikes!), and if you remove it you can add the others to each other, divide by 9, and the mean becomes 78.8888888888 (pretty much 79).