This Instructional Activity is a part of the Lesson 23, Unit 5, Grade 7. Students read the paragraph silently. In the previous lesson, you described how far apart the means of two data sets are in terms of the MAD (mean absolute deviation), a measure of variability. In this lesson, you will extend that idea to informally determine when two sample means computed from random samples are far enough apart from each other to imply that the population means also differ in a meaningful way. Recall that a meaningful difference between two means is a difference that is greater than would have been expected just due to sampling variability.