344 CHAPTER 7 Estimating Parameters and Determining Sample Sizes a. Find the sample size using the range rule of thumb to estimate s. b. Assume that s = 11.3 bpm, based on the value of s = 11.3 bpm for the sample of 153 male pulse rates. c. Compare the results from parts (a) and (b). Which result is likely to be better? 26. Mean Pulse Rate of Females Data Set 1 “Body Data” in Appendix B includes pulse rates of 147 randomly selected adult females, and those pulse rates vary from a low of 36 bpm to a high of 104 bpm. Find the minimum sample size required to estimate the mean pulse rate of adult females. Assume that we want 99% confidence that the sample mean is within 2 bpm of the population mean. a. Find the sample size using the range rule of thumb to estimate s. b. Assume that s = 12.5 bpm, based on the value of s = 12.5 bpm for the sample of 147 female pulse rates. c. Compare the results from parts (a) and (b). Which result is likely to be better? 27. Mean Grade-Point Average Assume that all grade-point averages are to be standardized on a scale between 0 and 4. How many grade-point averages must be obtained so that the sample mean is within 0.01 of the population mean? Assume that a 95% confidence level is desired. If we use the range rule of thumb, we can estimate s to be range>4 = 14 - 02>4 = 1. If conducting a telephone survey, does the sample size seem practical? 28. Mean Body Temperature Data Set 5 “Body Temperatures” in Appendix B includes 106 body temperatures of adults for Day 2 at 12 AM, and they vary from a low of 96.5°F to a high of 99.6°F. Find the minimum sample size required to estimate the mean body temperature of all adults. Assume that we want 98% confidence that the sample mean is within 0.1°F of the population mean. a. Find the sample size using the range rule of thumb to estimate s. b. Assume that s = 0.62°F, based on the value of s = 0.62°F for the sample of 106 body temperatures. c. Compare the results from parts (a) and (b). Which result is likely to be better? Appendix B Data Sets. In Exercises 29–32, use the Appendix B data sets to construct the confidence interval estimates of the mean. 29. Pulse Rates Refer to Data Set 1 “Body Data” and construct a 95% confidence interval estimate of the mean pulse rate of adult females; then do the same for adult males. Compare the results. 30. Second-Hand Smoke Refer to Data Set 15 “Passive and Active Smoke” and construct a 95% confidence interval estimates of the mean cotinine level in each of three samples: (1) people who smoke; (2) people who don’t smoke but are exposed to tobacco smoke at home or work; (3) people who don’t smoke and are not exposed to smoke. Measuring cotinine in people’s blood is the most reliable way to determine exposure to nicotine. What do the confidence intervals suggest about the effects of smoking and second-hand smoke? 31. New York Commute Time Refer to Data Set 31 “Commute Times” and use the 1000 New York commute times to construct a 95% confidence interval estimate of the population mean. 32. Los Angeles Commute Time Repeat Exercise 15 using all of the 1000 Los Angeles commute times from Data Set 31 “Commute Times” to construct a 99% confidence interval estimate of m.
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