66 Chapter 2 Graphical Summaries of Data CAUTION In a split stem-and-leaf plot, each stem must be given the same number of lines. 5 5 8 6 6 6 8 7 0 0 1 1 2 3 3 7 5 6 8 8 9 8 0 0 0 1 2 2 2 2 3 4 8 6 6 6 7 8 9 9 9 9 0 2 3 9 5 7 Figure 2.15 Split stem-and-leaf plot for the data in Table 2.16 Check Your Understanding 1. Weights of college students: The following table presents weights in pounds for a group of male college freshmen. 136 163 157 195 150 149 151 155 163 145 124 124 156 148 195 192 133 129 160 158 166 155 171 157 182 124 160 172 161 143 a. List the stems for a stem-and-leaf plot. b. For each item in the data set, write its leaf next to its stem. c. Rearrange the leaves in numerical order to create a stem-and-leaf plot. Answers are on page 74. Back-to-back stem-and-leaf plots When two data sets have values similar enough that the same stems can be used, we can compare their shapes with a back-to-back stem-and-leaf plot. In a back-to-back stemand leaf plot, the stems go down the middle. The leaves for one of the data sets go off to the right, and the leaves for the other go off to the left. EXAMPLE 2.14 Constructing a back-to-back stem-and-leaf plot In Table 2.15, we presented particulate emissions for 65 vehicles. In a related experiment carried out at the Colorado School of Mines, particulate emissions were measured for 35 vehicles driven at high altitude. Table 2.17 presents the results. Construct a back-to-back stem-and-leaf plot to compare the emission levels of vehicles driven at high altitude with those of vehicles driven at sea level. Table 2.17 Particulate Emissions for 35 Vehicles Driven at High Altitude 8.9 4.4 3.6 4.4 3.8 2.4 3.8 5.3 5.8 2.9 4.7 1.9 9.1 8.7 9.5 2.7 9.2 7.3 2.1 6.3 6.5 6.3 2.0 5.9 5.6 5.6 1.5 6.5 5.3 5.6 2.1 1.1 3.3 1.8 7.6
navidi_monk_essential_statistics_1e_ch1_3
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