HW9_skeleton

9.2

• 1. Decreases
• 2. False, it is centered at 0.
• 3. Alpha
• 4. False
• 5. False, the sample size can be large.
• 6. Robust
• 1. = 1.316

  2. = 1.697

  3. = 2.552

  4. = 1.725

• 13. x-bar = (18+24)/2 = 21, E = (23-18)/2 = 3
• 1. t0.02 = 2.172, Lower Bound = 103.66, Upper Bound = 112.34.

  2. t0.02 = 2.398, Lower Bound = 100.42, Upper Bound = 115.58. Decreasing the sample size increases the margin of error.

  3. t0.05 = 1.711, Lower Bound = 104.58, Upper Bound = 111.42. Decreasing the confidence level decreases the margin of error.

  4. No because the sample sizes are too small.

• 1. This statement is flawed because the interpretation implies the population has been provided for the population mean.

  2. This statement is correct because an interval has been provided for the population mean.

  3. This statement is flawed because the interpretation makes an implication about the individuals rather than the mean.

  4. This statement is flawed because the interpretation should be about the mean number of hours worked by adult Americans not about adults in Idaho.

• 29. t0.025 = 1.987. Lower bound = 317.63. Upper Bound = 394.57. We are 95% confident that the mean number of licks to the center of a tootise pop is between 317.63 and 394.57.
• 30. type answer here.

9.3

• 1. False, the chi-square distribution is skwewed to the right.
• 2. False
• 3. False, to construct a confidence interval about a population viariance or standard deviation, the sample must come from a normally distributed population.
• 4. False
• 5. x0.95 = 10.117, x0.05 = 30.144
• 1. x0.95 = 9.542, x0.05 = 30.144. Lower Bound = 7.94, Upper Bound = 23.66.

  2. x0.95 = 17.708, x0.05 = 42.557. Lower Bound = 8.59, Upper Bound = 20.63. The width of the interval decreases as the sample size increases.

  3. x0.99 = 7.633, x0.01 = 36.191. Lower Bound = 6.61, Upper Bound = 31.36. The width of the interval increases as the confidence level increases.

• 11. (s)^2 = (0.319)^2 = 0.102, x0.975 = 3.816. Lower Bound = 0.226, Upper Bound = 0.542. We can be 95% confident that the population standard deviation of the ph of rainwater in Tucker County, West Virginia is between 0.226 and 0.542.