Annual Consumption (in liters) 266 170 164 93 82 222 102 0 199 115 113 93 174 130 171 110 97 169 0 130 Chapter 8 7. The Wall Street Journal reported that automobile crashes cost the United States $162 billion annually. The average cost per person for crashes in the Tampa, FL was reported to be $1599. Suppose the average cost was based on a sample of 50 persons who had been involved in car crashes and that the population standard deviation is = $600. What is the margin of error for a 95% confidence interval? What would you recommend if the study required a margin of error of $150 or less? 9. AARP reported on a study conducted to learn how long it takes individuals to prepare their federal income tax return. The data contained in the file named TaxReturn (posted in our course) are consistent with the study results. These data provide the time in hours required for 40 individuals to complete their federal income tax returns. Using past years' data, the population can be assumed to be = 9 hours. What is the 95% confidence interval estimate of the mean time it takes an individual to complete a federal income tax return? 15. Sales personnel for Skillings Distributors submit weekly reports listing the customer contact made during the week. A sample of 65 weekly reports showed a sample mean of 19.5 customer contact per week. The sample std. deviation was 5.2. Provide 90% and 95% confidence intervals for the population mean number of weekly customer contacts for the sales personnel. 19. The average cost per night of a hotel room in New York City is $273. Assumes this estimate is based on a sample of 45 hotels and that the sample std. deviation is $65. a. With 95% confidence, what is the margin of error? b. What is the 95% confidence interval estimate of the population mean? c. Two years ago the average cost of a hotel room in New York City was $229. Discuss the change in cost over the two-year period. 21. Consumption of alcoholic beverages by young women of drinking age has been increasing in the United Kingdom, the United States and Europe. Data consistent with the finding reported are shown for a sample of 20 European women. 266, 170, 164, 93, 82, 222, 102, 0, 199, 115, 113, 93, 174, 130, 171, 110, 97, 169, 0, 130 Assume the population is roughly symmetric, construct a 95% confidence interval for the mean annual consumption of alcoholic beverages by European young women. 44. A sample survey of 54 discounted brokers showed that the mean price charged for a trade of 100 shares at $50 per share was $33.77. The survey is conducted annually. With the historic data available, assume a known population std. deviation of $15. a. Using the sample data, what is the margin of error associated with a 95% confidence interval? b. Develop a 95% confidence interval for the mean charged by discount brokers for a trade of 100 shares at $50 per share? 45. A survey conducted by the American Automobile Association showed that a family of four spends an average of $215.60 per day on vacation. Suppose a sample of 64 families of four vacationing at Niagara falls resulted in a sample mean of $252.45 per day and a sample std. deviation of $74.50. a. Develop a 95% confidence interval estimate of the mean amount spent per day by a family of four visiting Niagara Falls. b. Based on the confidence interval from part (a), does it appear that the population mean amount spent per day by families visiting Niagara Falls differs from the mean reported by the American Automobile Association? 49. A survey by Accountemps asked a sample of 200 executives to provide data on the number of minutes per day office workers waste trying to locate mislabeled, misfiles or misplaced items. Data consistent with this survey are contain in the file ActTemps (posted in the course). a. Use ActTemps to develop a point estimate of the number of minutes per day office workers waste trying to locate mislabeled, misfiles or misplaced items. b. What is the sample std. deviation? c. What is the 95% confidence interval for the mean number of minutes wasted per day? Return Preparation Time(Hours ) 35.3 30.5 37.4 26.5 13.0 49.9 28.8 44.0 61.6 0.5 40.5 34.9 47.9 36.6 24.1 39.8 47.8 18.5 36.6 39.2 14.5 37.3 40.5 49.3 45.5 28.3 19.5 5.6 52.6 41.4 45.3 39.0 33.7 29.4 14.5 40.1 33.7 36.9 5.6 33.7