This Instructional Activity is a part of the Lesson 17, Unit 5, Grade 7. In the example, students see a population of durations of time that people have spent at a gym. The times are displayed in the population tables at the end of the lesson. Convey to students that it is not practical to use all times to calculate the mean. It is important to make students aware of how unusual it would be to know all of the population values.