A68 ODD ANSWERS Cumulative Review for Chapters 3 –5 (page 294) 1. (a) np = 18.3 Ú 5, nq = 11.7 Ú 5 (b) 0.0778 (Tech: 0.0775) (c) Yes, because the probability is less than 0.05. 2. (a) 2.458 (b) 2.00 (c) 1.42 (d) 2.458 The size of an average household is about 2.5 persons. The standard deviation is 1.42, so most households differ from the mean by no more than about 1 person. 3. (a) 2.65 (b) 1.73 (c) 1.32 (d) 2.65 The number of fouls per game for DeMar DeRozan is about 2.65 fouls. The standard deviation is 1.32, so most of DeRozan’s games differ from the mean by no more than about 1 or 2 fouls. 4. (a) 0.795 (b) 0.574 (c) 0.692 5. (a) 43,680 (b) 0.019 6. 0.7642 7. 0.0010 8. 0.7995 9. 0.4984 10. 0.2862 11. 0.5905 12. (a) 0.1573 (b) 0.3556 (c) 0.000001 (d) The event in part (c) is unusual because the probability is less than 0.05. 13. (a) 0.0049 (b) 0.0149 (c) 0.9046 14. (a) 0.3288 (b) 0.8685 (c) Dependent P1Being a public school teacher 0 having 20 years or more of full-time teaching experience2 ≠ P1Being a public school teacher2 (d) 0.3730 15. (a) mx = 70, sx ≈ 0.190 (b) 0.0006 70.8 70 69.2 x Initial pressure (in psi) 16. (a) 0.0548 (b) 0.6547 (c) 52.2 months 17. (a) 495 (b) 0.002 18. (a) x P(x) 0 0.00002 1 0.00031 2 0.00284 3 0.01538 4 0.05465 5 0.13315 6 0.22528 7 0.26136 8 0.19899 9 0.08978 10 0.01823 (b) Probability Number of adults 0.1 0.2 0.3 012345678910 x P(x) Skewed Left (c) The values 0, 1, 2, 3, and 10 are unusual because their probabilities are less than or equal to 0.05. Chapter 6 Section 6.1 (page 305) 1. You are more likely to be correct using an interval estimate because it is unlikely that a point estimate will exactly equal the population mean. 3. d. As the level of confidence increases, zc increases, causing wider intervals. 5. 1.28 7. 1.15 9. -0.47 11. 1.76 13. 1.861 15. 0.192 17. c 18. d 19. b 20. a 21. (12.0, 12.6) 23. (9.7, 11.3) 25. E = 1.4, x = 13.4 27. E = 0.17, x = 1.88 29. 126 31. 7 33. E = 1.95, x = 28.15 35. (1348.98, 1459.20); (1338.43, 1469.75) With 90% confidence, you can say that the population mean price is between $1348.98 and $1459.20. With 95% confidence, you can say that the population mean price is between $1338.43 and $1469.75. The 95% CI is wider. 37. (43.70, 66.24); (41.55, 68.39) With 90% confidence, you can say that the population mean price is between $43.70 and $66.24. With 95% confidence, you can say that the population mean price is between $41.55 and $68.39. The 95% CI is wider. 39. Yes. The right endpoint of the 95% confidence interval is 1469.75. 41. No. The right endpoint of the 95% confidence interval is 68.39. 43. (a) An increase in the level of confidence will widen the confidence interval and the less certain you can be about a point estimate. (b) An increase in the sample size will narrow the confidence interval because it decreases the standard error. (c) An increase in the population standard deviation will widen the confidence interval because small standard deviations produce more precise intervals, which are smaller. 45. (32.1, 40.8); (29.7, 43.3) With 90% confidence, you can say that the population mean commute time is between 32.1 and 40.8 minutes. With 99% confidence, you can say that the population mean commute time is between 29.7 and 43.3 minutes. The 99% CI is wider. 47. 89
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