Review Exercises 517 Section 9.2 In Exercises 9–12, find the equation of the regression line for the data. Then construct a scatter plot of the data and draw the regression line. (Each pair of variables has a significant correlation.) Then use the regression equation to predict the value of y for each of the x-values, if meaningful. If the x-value is not meaningful to predict the value of y, explain why not. If convenient, use technology. 9. The average numbers (in thousands) of milk cows and the amounts (in billions of pounds) of milk produced in the United States for eight years (Source: U.S. Department of Agriculture) Milk cows, x 9224 9261 9320 9334 Milk produced, y 201.3 206.0 208.5 212.5 Milk cows, x 9406 9398 9337 9388 Milk produced, y 215.5 217.6 218.4 223.2 (a) x = 9080 cows (b) x = 9230 cows (c) x = 9340 cows (d) x = 9400 cows 10. The average times (in hours) per day spent watching television for adults ages 25 to 34 and adults ages 35 to 44 for 10 years (Source: U.S. Bureau of Labor Statistics) Adults ages 25 to 34, x 2.18 2.09 2.32 2.14 2.06 Adults ages 35 to 44, y 2.23 2.22 2.3 2.24 2.16 Adults ages 25 to 34, x 2.15 1.95 2.01 2.03 1.99 Adults ages 35 to 44, y 2.09 2.07 2.09 2.12 2.03 (a) x = 1.97 hours (b) x = 2.21 hours (c) x = 2.27 hours (d) x = 2.43 hours 11. The ages (in years) and the numbers of hours of sleep in one night for seven adults Age, x 35 20 59 42 68 38 75 Hours of sleep, y 7 9 5 6 5 8 4 (a) x = 16 years (b) x = 25 years (c) x = 85 years (d) x = 50 years 12. The engine displacements (in cubic inches) and the fuel efficiencies (in miles per gallon) of seven automobiles Displacement, x 170 134 220 305 109 256 322 Fuel efficiency, y 29.5 34.5 23.0 17.0 33.5 23.0 15.5 (a) x = 86 cubic inches (b) x = 198 cubic inches (c) x = 289 cubic inches (d) x = 407 cubic inches
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