472 CHAPTER 9 Correlation and Regression Duration, x Time, y Duration, x Time, y 1.80 56 3.78 79 1.82 58 3.83 85 1.90 62 3.88 80 1.93 56 4.10 89 1.98 57 4.27 90 2.05 57 4.30 89 2.13 60 4.43 89 2.30 57 4.47 86 2.37 61 4.53 89 2.82 73 4.55 86 3.13 76 4.60 92 3.27 77 4.63 91 3.65 77 TRY IT YOURSELF 2 A researcher conducts a study to determine whether there is a linear relationship between a person’s height (in inches) and pulse rate (in beats per minute). The data are shown in the table below. Display the data in a scatter plot and describe the type of correlation. Height, x 68 72 65 70 62 75 78 64 68 Pulse rate, y 90 85 88 100 105 98 70 65 72 Answer: Page A42 Constructing a Scatter Plot Using Technology Old Faithful, located in Yellowstone National Park, is the world’s most famous geyser. The durations (in minutes) of several of Old Faithful’s eruptions and the times (in minutes) until the next eruption are shown in the table at the left. Use technology to display the data in a scatter plot. Describe the type of correlation. SOLUTION MINITAB, Excel, the TI-84 Plus, and StatCrunch each have features for graphing scatter plots. Use such technology to draw the scatter plots shown. From the scatter plots, it appears that the variables have a positive linear correlation. MINITAB Time (in minutes) Duration (in minutes) 100 80 60 40 90 70 50 1 2 3 4 5 EXCEL Time (in minutes) Duration (in minutes) 100 80 60 40 90 70 50 1 2 3 4 5 TI-84 PLUS STATCRUNCH Time (in minutes) 2 60 70 80 90 2.5 3 3.5 4 4.5 Duration (in minutes) Interpretation As the durations of the eruptions increase, the times until the next eruption tend to increase. TRY IT YOURSELF 3 Consider the data on page 469 on the salaries and average home game attendances for the teams in Major League Baseball. Use technology to display the data in a scatter plot. Describe the type of correlation. Answer: Page A42 EXAMPLE 3
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