CASE STUDY Nutritionists tell us that a healthy diet should include 20 to 35 grams of fiber daily. Cereal manufacturers, hoping to attract health-conscious consumers, advertise their products as ”high-fiber’’ and other healthy options. The food label on the side of a box of cereal (mandated by the Food and Drug Administration) provides information that allows the consumer to choose a healthy breakfast cereal.

If you go to the breakfast cereal aisle of your local grocery store, you will find lots of different cereals displayed. You could examine all the boxes to see how much fiber each contains, but how do you make sense of all the numbers? Is your favorite cereal, Wheaties, with 3 grams of dietary fiber, among those with the highest fiber content? You could make a list of the fiber content of all the cereals, but it can be difficult to see patterns in large lists. As we saw in Chapter 10, graphs are a powerful way to make sense of large collections of numbers.

In this chapter, we will study two types of graphics—histograms and stemplots (also called stem-and-leaf plots)—that help us make sense of large lists. By the end of this chapter, you will know how to make them and what to look for when you study one of these graphs.