118 Chapter 3 Numerical Summaries of Data b. Assume the population is bell-shaped. Between what two values will approximately 68% of the population be? c. If we do not assume that the population is bell-shaped, at least what percentage of the population will be between 119 and 149? 29. The following TI-84 Plus display presents some sample statistics. a. Assume that a histogram of the sample is bell-shaped. Approximately what percentage of the sample values are between 104 and 248? b. Assume that a histogram for the sample is bell-shaped. Between what two values will approximately 68% of the sample be? c. If we do not assume that the histogram is bell-shaped, at least what percentage of the sample values will be between 68 and 284? 30. The following TI-84 Plus display presents some sample statistics. a. Assume that a histogram of the sample is bell-shaped. Approximately what percentage of the sample values are between 72 and 86? b. Assume that a histogram for the sample is bell-shaped. Between what two values will approximately 95% of the sample be? c. If we do not assume that the histogram is bell-shaped, at least what percentage of the sample values will be between 65 and 93? Working with the Concepts 31. Gas prices: The following table presents the average price, in U.S. dollars per gallon, of unleaded regular gasoline in several countries in the years 2001 and 2007. Country 2001 2007 Australia 1.71 3.85 Canada 1.72 3.59 China 1.22 2.29 Germany 3.40 6.88 Japan 3.27 4.49 Mexico 2.20 2.40 South Korea 3.76 6.21 Taiwan 2.02 3.20 United States 1.46 2.80 Source: U.S. Department of Energy a. Find the sample standard deviation of the gas prices for 2001. b. Find the sample standard deviation of the gas prices for 2007. c. Gas prices increased between 2001 and 2007. Did the spread in gas prices increase as well? 32. Sports car or convertible? The following table presents the fuel efficiency, in miles per gallon, for a sample of convertibles and a sample of sports cars. Convertible Model MPG Sports Model MPG Volkswagen Eos 25 BMW 135i 23 Mini Cooper 25 Mazda3 Mazdaspeed 24 Saab 9-3 24 Subaru Impreza WRX STi 21 BMW 328i 21 Mazda RX-8 18 Toyota Camry Solara 21 Mitsubishi Lancer Evolution 21 Volvo C70 21 Volkswagen GTI 25 Ford Mustang V6 20 Honda Civic Si 27 Source: Consumer Reports a. Find the sample standard deviation of the mileage for the sample of convertibles. b. Find the sample standard deviation of the mileage for the sample of sports cars. c. Which sample has greater spread? 33. Heavy football players: Following are the weights, in pounds, for samples of offensive and defensive linemen in the National Football League at the beginning of the 2010 season. Offense: 335 301 307 252 260 307 325 310 305 305 264 325 Defense: 284 290 286 355 305 295 297 325 310 297 314 348
navidi_monk_essential_statistics_1e_ch1_3
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