Can my tutor please explain and answer all of the following question, please show your work.
Chapter 7.1 9. Fuel Efficiency of Cars and Trucks Since 1975 the average fuel efficiency of U.S. cars and light trucks (SUVs) has increased from 13.5 to 25.8 mpg, an increase of over 90%! A random sample of 40 cars from a large community got a mean mileage of 28.1 mpg per vehicle. The population standard deviation is 4.7 mpg. Estimate the true mean gas mileage with 95% confidence. Source: World Almanac 2012. of the population is 4.2 pounds. IL. Overweight Men For a random sample of 60 overweight men, the mean of the number of pounds that they were overweight was 30. The standard deviation a. Find the best point estimate of the average number of excess pounds that they weighed b. Find the 95% confidence interval of the mean of these pounds. c. Find the 99% confidence interval of these pounds. d. Which interval is larger? Why? 16. Number of Farms A random sample of the number of farms (in thousands) in various states follows. Estimate the mean number of farms per state with 90% confidence. Assume o - 31.0. 95 90 54 68 49 44 79 80 48 16 109 40 Source: New York Times Almanac. 18. Day Care Tuition A random sample of 50 four-year-olds attending day care centers provided a yearly tuition average of $3987 and the population standard deviation of $630. Find the 90% confidence interval of the true mean. If a day care center were starting up and wanted to keep tuition low, what would be a reasonable amount to charge? 21. Christmas Presents How large a sample is needed to estimate the population mean for the amount of money a person spends on Christmas presents within $2 and be 95% confident? The standard deviation of the population is $7.50. 23. Internet Viewing A researcher wishes to estimate the average number of minutes per day a person spends on the Internet. How large a sample must she select if she wishes to be 90% confident that the population mean is within 10 minutes of the sample mean? Assume the population standard deviation is 42 minutes. 25. Water Temperature If the variance of the water temperature in a lake is 280, how many days should the researcher select to measure the temperature to estimate the true mean within 30 with 99% confidence? Chapter 7.2 3. Find the values for each. a. tala and n = 18 for the 99% confidence interval for the mean b. tala and n = 23 for the 95% confidence interval for the mean C. tala and n = 15 for the 98% confidence interval for the mean d. to and n = 10 for the 90% confidence interval for the mean e. t and n = 20 for the 95% confidence interval for the mean 9. Calories in Candy Bars The number of calories per candy bar for a random sample of standard-size candy bars is shown below. Estimate the mean number of calories per candy bar with 98% confidence. 220 220 210 230 275 260 240 260 220 240 240 280 230 280 II. Weights of Elephants A sample of 8 adult elephants had an average weight of 12,300 pounds. The standard deviation for the sample was 22 pounds. Find the 95% confidence interval of the population mean for the weights of adult elephants. 13. Work Time Lost due to Accidents At a large company, the Director of Research found that the average work time lost by employees due to accidents was 98 hours per year. She used a random sample of 18 employees. The standard deviation of the sample was 5.6 hours. Estimate the population mean for the number of hours lost due to accidents for the company, using a 95% confidence interval 5. Stress Test Results For a group of 12 men subjected to a stress test situation, the average heart rate was 109 beats per minute. The standard deviation was 4. Find the 99% confidence interval of the population mean. 17. Costs for a 30-Second Spot on Cable Television The approximate costs for 30-second randomly selected spots for various cable networks in a random selection of cities are shown. Estimate the true population mean cost for a 30-second advertisement on cable network with 90% confidence. 14 165 15 66 23 30 150 22 12 13 54 73 41 78 Source: www.spotrunner.com
