56 CHAPTER 2 Descriptive Statistics TRY IT YOURSELF 1 Use a stem-and-leaf plot to organize the points scored by the 55 winning teams listed on page 39. Describe any patterns. Answer: Page A36 Constructing Variations of Stem-and-Leaf Plots Organize the data set in Example 1 using a stem-and-leaf plot that has two rows for each stem. Describe any patterns. SOLUTION Use the stem-and-leaf plot from Example 1, except now list each stem twice. Use the leaves 0, 1, 2, 3, and 4 in the first stem row and the leaves 5, 6, 7, 8, and 9 in the second stem row. The revised stem-and-leaf plot is shown. Notice that by using two rows per stem, you obtain a more detailed picture of the data. Number of Text Messages Sent 1 Key: 100 4 = 104 1 7 8 2 0 3 4 2 5556799 3 002233 3 5 6 8 4 0 1 2 3 4 6 9 9 5 2 4 5 5 9 6 6 6 8 9 7 3 7 5 5 6 8 8 0 1 4 8 8 9 9 8 10 4 10 9 11 4 11 12 3 12 13 13 14 14 8 Interpretation From the display, you can see that most of the cell phone users sent between 20 and 80 text messages. TRY IT YOURSELF 2 Using two rows for each stem, revise the stem-and-leaf plot you constructed in Try It Yourself 1. Describe any patterns. Answer: Page A36 EXAMPLE 2 Tech Tip You can use technology such as Minitab, StatCrunch, or Excel (with the XLSTAT add-in) to construct a stem-and-leaf plot. For instance, a StatCrunch stem-and-leaf plot for the data in Example 1 is shown below. STATCRUNCH Variable: Number of text messages sent Decimal point is 1 digit(s) to the right of the colon. Leaf unit = 1 1 : 78 2 : 0345556799 3 : 002233568 4 : 0123699 5 : 2459 6 : 689 7 : 35568 8 : 0148 9 : 8 10 : 49 11 : 4 12 : 3 13 : 14 : 8 Study Tip You can use stem-and-leaf plots to identify unusual data entries called outliers. In Examples 1 and 2, the data entry 148 is an outlier. You will learn more about outliers in Section 2.3.
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