What you’ll learn to do: calculate and interpret standard deviation and z-scores

In addition to understanding the center of a distribution, it is helpful to know how much variation there is from the center of the distribution. Airlines might want to know the typical weight of a customer to help them predict the total weight of the customers on a plane. However, they may also want to know how much variability there is in that typical weight. Standard deviation and variance are ways to describe variability in a distribution.