506 CHAPTER 9 Correlation and Regression 16. Voter Turnout The U.S. voting age populations (in millions) and the number of ballots cast (in millions) for the highest office in federal elections for ten nonpresidential election years are shown in the table. The equation of the regression line is ny = 0.429x - 10.763. (Source: United States Elections Project) Voting age population, x 166.0 177.9 186.2 195.3 205.3 Ballots cast in federal elections, y 67.6 65.0 67.9 75.1 72.5 Voting age population, x 215.5 225.5 236.0 245.7 255.8 Ballots cast in federal elections, y 78.4 83.8 89.1 81.7 117.1 17. Natural Gas The table shows the marketed productions of natural gas (in billions of cubic feet) in the United States and the exports of natural gas (in billions of cubic feet) from the United States for seven years. The equation of the regression line is ny = 0.355x - 7960.686. (Source: U.S. Energy Information Administration) Marketed production, x 27,498 28,772 28,400 29,238 33,009 36,515 36,173 Export, y 1514 1784 2335 3154 3608 4656 5284 18. Fund Assets The table shows the total assets (in billions of dollars) of individual retirement accounts (IRAs) and federal defined benefit (DB) plans for ten years. The equation of the regression line is ny = 0.122x + 558.880. (Source: Investment Company Institute) IRAs, x 5550 6123 6961 7400 7610 Federal DB plans, y 1220 1288 1364 1425 1504 IRAs, x 8415 9395 9925 9365 12,555 Federal DB plans, y 1589 1679 1781 1895 2006 19. New Vehicle Sales The table shows the numbers of new vehicle sales (in thousands) in the United States for Ford and General Motors for 11 years. The equation of the regression line is ny = 0.937x + 637.674. (Source: NADA Industry Analysis Division) New vehicle sales (Ford), x 1942 1656 1905 2111 2206 2435 New vehicle sales (General Motors), y 2956 2072 2211 2504 2596 2786 New vehicle sales (Ford), x 2418 2549 2542 2513 1968 New vehicle sales (General Motors), y 2935 3082 3042 3000 2536
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