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Quiz 8: Confidence Intervals

Module by: Susan Dean, Barbara Illowsky, Ph.D.. E-mail the authors

Summary: This module is a quiz containing 10 multiple choice questions covering topics related to confidence intervals. This module is part of a set of companion resources to Collaborative Statistics (col10522) by Barbara Illowsky and Susan Dean.

Exercise 1

When constructing a confidence interval for the population mean, the case where the population standard deviation is known is __________.

  • A. possible, and the most common
  • B. possible, but not common
  • C. possible, and quite common
  • D. impossible

Exercise 2

When constructing a Confidence Interval, which case is preferable?

  • A. large confidence level, small confidence interval
  • B. small confidence level, small confidence interval
  • C. small confidence level, large confidence interval
  • D. large confidence level, large confidence interval

Exercise 3

Which of the following is NOT a point estimate?

  • A. x-bar
  • B. p-hat or p-prime
  • C. s
  • D. sigma

Exercise 4

When should the Student-t distribution be used in constructing a confidence interval for the population mean?

  • A. When the population proportion is known and the underlying population is normally distributed.
  • B. When the population standard deviation is unknown and the underlying population is normally distributed.
  • C. When the population proportion is unknown and the underlying population is normally distributed.
  • D. When the population standard deviation is known and the underlying population is normally distributed.

Exercise 5

When constructing a Confidence Interval for the population mean and both the sample standard deviation and the population standard deviation are known, which of the following should be used?

  • A. normal distribution using the sample standard deviation
  • B. normal distribution using the population standard deviation
  • C. student-t distribution using the population standard deviation
  • D. student-t distributuion using the sample standard deviation

Exercise 6

A study was done to determine the proportion of voters that feel that their local government is doing an adequate job. Of the 160 voters surveyed, 144 feel that their local government is doing an adequate job. Calculate the 95% confidence interval for the true proportion of voters that feel that their government is doing an adequate job.

  • A. (0.85, 0.95)
  • B. 0.90
  • C. (0.80, 1.00)
  • D. (144, 160)

Exercise 7

To reduce the error bound in a future study, which of the following should be done?

  • A. increase the sample size n
  • B. decrease the sample size n
  • C. conduct a biased survey
  • D. increase the confidence level

Exercise 8

A study was done to determine the average number of homes that a homeowner owns in his or her lifetime. For the 60 homeowners surveyed, the sample average was 4.2 and the sample standard deviation was 2.1. Calculate the 95% confidence interval for the true average number of homes that a person owns in his or her lifetime.

  • A. (3.90, 4.50)
  • B. (3.66, 4.74)
  • C. (4.01, 4.39)
  • D. (3.67, 4.73)

Exercise 9

A study was done to determine the average number of homes that a homeowner owns in his or her lifetime. For the 60 homeowners surveyed, the sample average was 4.2 and the sample standard deviation was 2.1. The distribution to use to calculate the 95% confidence interval is ________________.

  • A. Exponential
  • B. Student-t with df = 59
  • C. Student-t with df = 60
  • D. Binomial

Exercise 10

Calculate the error bound for a survey in which the sample mean is 5, the population standard deviation is 3, the confidence level is 0.90, and the number surveyed is 12.

  • A. 1.56
  • B. 1.42
  • C. (3.58, 6.42)
  • D. (3.44, 6.56)

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