In this lesson, students consider another measure of center, the median. They make use of the structure of the data set (MP7) to see that the median partitions the data into two halves: One half of the values in the data set has that value or smaller values, and the other half has that value or larger. Students learn how to find the median for data sets with both an even and an odd number of values. 

Students interpret the median of a distribution in context (MP2) and recognize the difference in meaning between the median and mean of a distribution.

Then students investigate whether the mean or the median is a more appropriate measure of the center of a distribution in a given context. They learn that when the distribution is symmetrical, the mean and median have similar values, so the mean should usually be used for its connection to fairness. When a distribution is not symmetrical, however, the mean is often greatly influenced by values that are far from the majority of the data points. In this case, the median may be a better choice.