778 CHAPTER 12 Statistics Solution By quickly glancing at the data, we can see the ages consist of two-digit numbers. Let’s use the first digit, the tens digit, as our stem and the second digit, the units digit, as the leaf. For example, for an age of 62, the stem is 6 and the leaf is 2. Our values are numbers in the 20s, 30s, 40s, 50s, 60s, and 70s. Therefore, the stems will be 2, 3, 4, 5, 6, 7 as shown below. 2 3 4 5 6 7 Next we place each leaf on its stem. We will do so by placing the second digit of each value next to its stem, to the right of the vertical line. Our first value is 29. The 2 is the stem and the 9 is the leaf. Therefore, we place a 9 next to the stem of 2 and to the right of the vertical line. 2 9 The next value is 31. We will place a leaf of 1 next to the stem of 3. 2 3 9 1 The next value is 39. Therefore, we will place a leaf of 9 after the leaf of 1 that is next to the stem of 3. 2 3 9 1 9 We continue this process until we have listed all the leaves on the display. The diagram below shows the stem-and-leaf display for the ages of the visitors. In our display, we will also include a legend to indicate the values represented by the stems and leaves. For example, 5 6 represents 56. 5 6 represents 56 2 3 4 5 6 7 9 7 8 1 9 2 3 7 4 5 4 6 9 8 0 0 2 8 1 2 ⎧ ⎨ ⎪ ⎪ ⎪ ⎩ ⎪ ⎪ ⎪ ⎫ ⎬ ⎪ ⎪ ⎪ ⎭ ⎪ ⎪ ⎪ Now try Exercise 29 Stems Leaves 7 Every piece of the original data can be seen in a stem-and-leaf display. From the above diagram, we can see that five of the visitors’ ages were in the 40s. Only two visitors were older than 70. Note that the stem-and-leaf display gives the same visual impression as a sideways histogram. Circle Graphs Circle graphs (also known as pie charts) are often used to compare parts of one or more components of the whole to the whole. A random sample of 500 consumers were asked how they pay for their purchases. The circle graph in Fig. 12.11 shows
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