HW9_skeleton

9.2

• 1. Decreases
• 2. False
• 3. α
• 4. True
• 5. False
• 6. robust
• 1. 1.316

  2. 1.697

  3. 2.552

  4. 1.725

• 1. 2.205

  2. 1.309

  3. 1.943

  4. 2.120

• 13. x̅=21 ME=3
• 14. x̅=25 ME=5
• 1. (103.66,112.34)

  2. (100.42,115.58), Decreasing the sample size increases the margin of error.

  3. (104.58,111.42), Decreasing the level of confidence decreases the margin of error.

  4. No, because the sample sizes were not greater than 30 (not large enough).

• 1. Choice A is flawed because it implies that the mean varies rather than the interval.

  2. Choice B is a reasonable interpretation.

  3. Choice C is flawed because it implies that the population of adult Americans is changing rather than the mean.

  4. Choice D is flawed because it incorrectly identifies the population.

• 29. (317.63,394.57), We are 95% confident that the number of licks required to reach the candy center of a Tootsie Pop is between 317.63 and 394.57.
• 30. (12.05, 14.75), We are 99% confident that the mean number of books that Americans read either all or part of during the preceding year lies between 12.05 and 14.75.

9.3

• 1. False
• 2. True
• 3. False
• 4. False
• 5. The two critical values are 10.117 and 30.114.
• 6. The two critical values are 12.401 and 39.364.
• 1. (7.94, 23.66)

  2. (8.59, 20.63), The width of the interval decreases as the sample size increases.

  3. (6.61, 31.36), The width of the interval increases as the confidence level increases.

• 11. (0.23, 0.54), We are 95% confident that the standard deviation pH of rainwater in Tucker County, West Virginia is between 0.23 and 0.54.