Unit 8, Lesson 11
Comparing Groups
Grade 7
Preparation
Lesson Narrative
In this lesson, students review measures of center and variability from grade 6. They also work to informally decide whether or not two distributions are very different from each other (MP3). This lesson introduces the idea of expressing the difference between the centers of two distributions as a multiple of a measure of variability as a way to help students make this determination (MP2).
An optional activity provides additional practice comparing two groups based on their means and mean absolute deviations.
- Calculate the mean and mean absolute deviation for a data set, and interpret (orally) these measures.
- Compare and contrast (orally and in writing) populations represented on dot plots in terms of their shape, center, spread, and visual overlap.
- Justify (in writing) whether two populations are “very different” based on the difference in their means expressed as a multiple of the mean absolute deviation.
Let’s compare two groups.
Required Preparation
None
The mean is one way to measure the center of a data set. It can be thought of as a balance point. To find the mean, add all the numbers in the data set. Then divide by how many numbers there are.
- Data set: 7, 9, 12, 13, 14
- Add values:
- Divide by number of values:
The mean is 11. So, the typical travel time is 11 minutes.