Exercises on Confidence Intervals

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NOTE: If you are using a TI-83 or more accurate t-tables, select the closest response. For each question, make sure you are using the correct distribution!

1. The heights of adult women are normally distributed. A sample of 32 women yields a mean of 64.82 and a standard deviation of 3.45. Construct a 95% confidence interval for the true mean height of adult women.

  (63.62 < mu < 66.02).
  (63.25 < mu< 66.39).
  (63.40 < mu < 66.24).
  (63.82 < mu < 65.82).


2. A package of 46 M & M's yields 52.1% brown M & M's. Construct a 96% confidence interval for the true population proportion of brown M & M's.

  (0.448 < p < 0.594).
  (0.370 < p < 0.673).
  (0.331 < p < 0.711).
  (0.349 < p < 0.693).


3. The heights of adult men are normally distributed. A sample of 10 men yields a mean of 70.90 and a standard deviation of 4.20. Construct a 95% confidence interval for the true mean height of adult men.

  (68.30 < mu < 73.50).
  (67.90 < mu < 73.90).
  (68.72 < mu <73.08).
  (68.47 <mu <73.33 ).


4. Simon Newcomb measured the time required for light to travel from his laboratory on the Potomac River to a mirror at the base of the Washington Monument and back, a total distance of about 7400 meters. The original data set, with an outlier deleted, was normally distributed. A random sample of 35 times resulted in a mean of 27.03 seconds and a standard deviation of 7.16. Construct a 95% confidence interval for the true speed of light. websight is http://lib.stat.cmu.edu/DASL/Stories/EstimatingtheSpeedofLight.html"

  (25.04 < mu < 29.02).
  (24.66 < mu < 29.40).
  (24.21 < mu< 29.85).
  (23.92 < mu < 30.14).


5. The area in square miles of each county in New Jersey is normally distributed. A random sample of 5 counties yields a mean of 331.6 sq.mi. and a standard deviation of 316.9 sq. mi. What is a 90% confidence interval for the true population mean? The websight is http://lib.stat.cmu.edu/DASL/Stories/SizeofCountiesinNewJersey.html.

  (150.2 < mu < 513.0).
  (98.5 < mu < 564.7).
  (53.8 < mu < 609.4).
  (29.4 < mu < 633.8).


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Copyright © 1998 Donna Tupper.