A number that is calculated to summarize a group of numbers. The most commonly used average is the mean, the sum of the numbers divided by however many numbers there are in the group. The median is the middle value in a group of numbers ranked in order of size. The mode is the number that occurs most often in a group of numbers. Take the following group of numbers: 1, 2, 2, 9, 12, 13, 17

The mean is 56/7=8

The median is 9

The mode is 2