Module 8 Lesson 2: Statistical Variability and Comparing Pop

Mean - also called the average of a set of numbers. To find the mean (average) add up all the numbers and divide by how many numbers there are in the set.

Mean Absolute Deviation (MAD) - The average distance of each data point from the mean (average). View the video on page 3 of lesson 2 for a good explanation of how to find the MAD.

Variability - describes how the data points are spread out from the average

Range - the distance between the smallest and largest data points

It indicates how spread out the data is from the mean (average)

A small MAD number means that the data points are close to each other. For example, the set 1,2,3,4 has a MAD value of 1. This means the data points are close together - less variability in the data set

A large MAD number means the data points are more spread out. For example, the set 1, 20, 100, 300 has a MAD value of 114.75. This high number means that the data is not close together and is spread out - more variability in the data set

Tells us how spread out the data is

To find the range subtract the smallest number from the largest

For Example: Fred's score on five tests were 60, 95, 100, 85 75. To find his range of scores subtract the smallest number from the largest 100-60 = 40. The number 40 is the range of his scores.

Gives us a basic idea of how spread out the data is, to get a more precise calculation for variability we would need to find the MAD.