HW9_skeleton

9.2

• 1. Decreases.
• 2. False. It is centered at zero.
• 3. α.
• 4. True.
• 5. False, it can also be large.
• 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. Point Estimate= 21. Margin of Error= 3.
• 14. Point Estimate= 24. Margin of Error= 5.
• 1. T=2.172. Lower=103.66 Upper=112.344

  2. Decreasing the sample size increases the margin of error. T=2.398 Lower=100.417 Upper= 115.583

  3. Decreasing the level of confidence decreases the margin of error. T=1.711 Lower=104.578 Upper=111.422

  4. No because the sample sizes are too small.

• 1. Wrong.The population mean of this answer varies rather than the interval. Also its confidence, not probabiliy.

  2. Correct. Interval provided for population mean.

  3. Wrong.This answer is saying that 95% of the population has a certain charachteristic, when it should be 95% CONFIDENCE. They are making an implication about the population rather than the mean.

  4. Wrong. The answer provided talks about adults in idaho, when the survey taken by a sample about adult americans.

• 29. (317.631,394.569). We are 95% confident that the mean number of licks it takes to get to the center of a tootsie pop is between 317.631 and 394.569.
• 30. T= 2.581. Upper/lower= (12.049, 14.751). We are 99% confident that the mean number of americans who read all or partly through paper or hardback books in the past year is between 12.049 and 14.751.

9.3

• 1. False.
• 2. True.
• 3. False. Population needs to be normal.
• 4. False.
• 5. .05=30.144., .95=10.117
• 6. .025=39.364 , .975=12.401
• 1. (7.941, 23.663)

  2. Decreasing the sample size decreases the width. (8.59, 20.63)

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

• 11. (.2258, .5412) We are 90% confident that the pop standard deviation for the PH levels in Tucker county is between .2258 and .5412