MTH 232 Section 13.2 Measuring the Center and Variation of Data Overview • The center of a data set can be defined in three ways: 1. Mean 2. Median 3. Mode Mean • Also referred to as the arithmetic mean, or average. • Add up the data values, then divide by the number of data values. • Can be modeled using manipulatives. • May or may not be the “best” center, depending on the number and quality of outliers. Median • The “middle” of the data when the values are arranged from smallest to largest. • The number of data values to the left of the median will be equal to the number of data values to the right of the median. • Be sure to reference the “other” definition of median as a way to help students remember. • Lining up students from shortest to tallest is a good activity to demonstrate median (be careful to use an odd number of students). • Median is unaffected by outliers. Mode • The data value (or values) that appears (or appear) the most. • It is possible for a data set to have more than one mode. • It is also possible for a data set to not have a mode. • Mode is unaffected by outliers. Let’s “Describe” our Class! • What “value” do we want to use? • For the chosen measure, find the mean, median and mode. • Which measure of central tendency best describes us? • Add to homework set: 17, 18, 19