University of Regina Suppose that you are in some course and have just received your grade on an exam. It is natural to ask how the rest of the class did on the exam so that you can put your grade in some context.
Lets look at a small example.
One measure of the variation is the range, which is the difference between the highest and lowest grades. The range is not a very good measure of variation here as classes 1 and 2 have the same range yet their variation seems to be quite different. It is this concept that leads to the definition of the standard deviation. Lets look at class 1. For each student calculate the difference between the students grade and the mean.