Section 2.4 Graphs Can Be Misleading 77 Check Your Understanding 1. The population of country A is twice as large as the population of country B. True or false: If images are used to represent the populations, both the height and width of the image for country A should be twice as large as the height and width of the image for country B. 2. If the baseline of a bar graph or time-series plot is not at zero, then the differences may appear to be than they actually are. (Choices: larger, smaller) Answers are on page 80. Objective 3 Understand how three-dimensional graphs can be misleading Three-Dimensional Graphs and Perspective Figure 2.23 presented a bar graph that presented an accurate picture of the prices of jet fuel in the years 2000 and 2008. Newspapers and magazines often prefer to present threedimensional bar graphs, because they are visually more impressive. Unfortunately, in order to make the tops of the bars visible, these graphs are often drawn as though the reader is looking down on them. This can make the bars look shorter than they really are. Figure 2.24 presents a three-dimensional bar graph of the sort often seen in publications. The data are the same as in Figure 2.23: The price in 2000 is $0.90, and the price in 2008 is $3.16. However, because you are looking down on the bars, they appear shorter than they really are. 4.00 3.00 2.00 1.00 0 Price of Jet Fuel in Dollars per Gallon 2000 2008 Figure 2.24 Price per gallon of jet fuel in 2000 and 2008. The bars appear shorter than they really are, because you are looking down at them. Beware of three-dimensional bar graphs. If you can see the tops of the bars, they may look shorter than they really are. SECTION 2.4 Exercises Exercises 1 and 2 are the Check Your Understanding exercises located within the section. Understanding the Concepts In Exercises 3 and 4, fill in each blank with the appropriate word or phrase. 3. A plot that represents how much of something there is may be misleading if the baseline is not at . 4. The area principle says that when images are used to compare amounts, the areas of the images should be to the amounts. Working with the Concepts 5. CD sales decline: Sales of CDs have been declining for several years as more music is downloaded over the Internet. Following are two bar graphs that illustrate the decline in CD sales. (Source: Recording Industry Association of America)
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