According to Oxford University's Medical Sciences Division, the mean is the average value of a group of numbers, the median is the middle value in an ordered list of values and the mode is the most common number that appears in that numerical group or list. So, for a list of values such as 2, 3, 3, 6, 7, 8, 11, the mean (or average) would be 5.71, the median (or middle value) would be 6 and the mode (or most common value) would be 3.
The mean of a set of numbers is calculated by adding all of the numbers together and dividing by the number of numbers given. In the example above, the sum of the seven numbers is 40; when divided by seven, the number of values given, the correct answer is calculated. This is the only value of the three that requires arithmetic.