Bluman A.G. Elementary Statistics- A Step By Step Approach

82 Chapter 2 Frequency Distributions and GraphsFigure 2–22 shows that the distribution peaks in the center and that there are no gapsin the data. For 7 of the 20 days, the number of patients receiving cardiograms wasbetween 31 and 36. The plot also shows that the testing center treated from a minimumof 2 patients to a maximum of 57 patients in any one day.If there are no data values in a class, you should write the stem number and leave theleaf row blank. Do not put a zero in the leaf row.Example 2–14An insurance company researcher conducted a survey on the number of carthefts in a large city for a period of 30 days last summer. The raw data areshown. Construct a stem and leaf plot by using classes 50–54, 55–59, 60–64, 65–69,70–74, and 75–79.52 62 51 50 6958 77 66 53 5775 56 55 67 7379 59 68 65 7257 51 63 69 7565 53 78 66 55Figure 2–23Stem and Leaf Plot forExample 2–1455667705252515353516672768377938899 9SolutionStep 1 Arrange the data in order.50, 51, 51, 52, 53, 53, 55, 55, 56, 57, 57, 58, 59, 62, 63,65, 65, 66, 66, 67, 68, 69, 69, 72, 73, 75, 75, 77, 78, 79Step 2Step 3Separate the data according to the classes.50, 51, 51, 52, 53, 53 55, 55, 56, 57, 57, 58, 5962, 63 65, 65, 66, 66, 67, 68, 69, 69 72, 7375, 75, 77, 78, 79Plot the data as shown here.Leading digit (stem) Trailing digit (leaf)5 0 1 1 2 3 35 5 5 6 7 7 8 96 2 36 5 5 6 6 7 8 9 97 2 37 5 5 7 8 9The graph for this plot is shown in Figure 2–23.Interesting FactThe average numberof pencils and indexcards David Lettermantosses over hisshoulder during oneshow is 4.When the data values are in the hundreds, such as 325, the stem is 32 and the leafis 5. For example, the stem and leaf plot for the data values 325, 327, 330, 332, 335, 341,345, and 347 looks like this.32 5 733 0 2 534 1 5 7When you analyze a stem and leaf plot, look for peaks and gaps in the distribution.See if the distribution is symmetric or skewed. Check the variability of the data by lookingat the spread.2–48