Description: The mean (average) of a data set is found by adding all numbers in the data set and then dividing by the number of values in the set. The median is the middle value when a data set is ordered from least to greatest. The mode is the number that occurs most often in a data set. Created by Sal Khan. We will now begin our journey into the world of statistics, which is really a way to understand or get our head around data. So if we have a bunch of data, and if we want to tell something about all of that data without giving them all of the data, can we somehow describe it with a smaller set of numbers? So with that out of the way, let's think about how we can describe data.*Teacher Advisor is 100% free.