CHAPTER 12 Review Exercises 839 c) What is a cluster sample? A cluster sample consists of dividing the population into sections. Then randomly select sections to use and either select all the items in the selected sections or a random sample of items from the selected sections. d) What is a stratified sample? A stratified sample consists of dividing the population into strata and then taking a random sample from each strata. e) What is a convenience sample? A convenience sample uses data that are easily or readily obtained. In Exercises 3 and 4, tell what possible misuses or misinterpretations may exist in the statements. 3. The Stay Healthy Candy Bar indicates on its label that it has no cholesterol. Therefore, it is safe to eat as many of these candy bars as you want. The candy bars may have lots of calories, or fat, or sodium. Therefore, it may not be healthy to eat them. 4. JanSport sells more backpacks than Columbia. Therefore, JanSport is a more profitable company than Columbia. Sales may not necessarily be a good indicator of profit. Expenses must also be considered. 5. Amazon Prime Subscriptions in the United States In 2021, there were 151.9 million Amazon Prime subscribers in the United States. In 2022, there were 157.4 million Amazon Prime subscribers in the United States. Draw a bar graph that appears to show a a) small increase in the number of Amazon Prime subscribers from 2021 to 2022. * b) large increase in the number of Amazon Prime subscribers from 2021 to 2022. * 12.2 6. Consider the following set of data. 35 37 38 41 43 36 37 38 41 43 36 37 39 41 43 36 37 39 41 44 37 37 39 42 45 a) Construct a frequency distribution letting each class have a width of 1. * b) Construct a histogram of the frequency distribution. * c) Construct a frequency polygon of the frequency distribution on the same set of axes as the histogram. * 7. Average Monthly High Temperature Consider the following average monthly high temperature in July for 40 selected U.S. cities. 71 79 58 73 80 75 84 77 82 72 80 70 75 66 73 72 80 66 74 68 81 84 75 67 91 76 82 79 63 69 68 79 71 76 80 83 73 87 82 71 a) Construct a frequency distribution. Let the first class be 58–62. * b) Construct a histogram of the frequency distribution. * c) Construct a frequency polygon of the frequency distribution on the same set of axes as the histogram. * d) Construct a stem-and-leaf display. * 12.3, 12.4 In Exercises 8–13, use the following test scores: 65 72 77 81 , , , , 82 91 , . Determine the 8. mean. 78 9. median. 79 10. mode. No mode 11. midrange. 78 12. range. 26 13. standard deviation. 80 8.94 ≈ In Exercises 14–19, for the set of data: 9 10 17 19 24 12 , , , , , , 17 28 12 22 20 26 , , , , , , determine the 14. mean. 18 15. median. 18 16. mode. 12 and 17 17. midrange. 18.5 18. range. 19 19. standard deviation. 40 6.32 ≈ 12.5 Police Response Time In Exercises 20–24, assume that police response time to emergency calls is normally distributed with a mean of 9 minutes and a standard deviation of 2 minutes. Determine the percent of emergency calls with a police response time 20. between 7 and 11 minutes. 68.26% 21. between 5 and 13 minutes. 95.44% 22. less than 12.2 minutes. 94.52% 23. more than 12.2 minutes. 5.48% 24. more than 7.8 minutes. 72.57% Pizza Delivery In Exercises 25– 28, assume that the amount of time to prepare and deliver a pizza from Pepe’s Pizza is normally distributed with a mean of 20 minutes and standard deviation of 5 minutes. Determine the percent of pizzas that were prepared and delivered 25. between 20 and 25 minutes. 34.13% 26. in less than 18 minutes. 34.46% 27. between 22 and 28 minutes. 28.98% 28. If Pepe’s Pizza advertises that the pizza is free if it takes more than 30 min to deliver, what percent of Pepe’s pizza delivery orders will be free? 2.28% *See Instructor Answer Appendix
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