Start learning →

AP Statistics Confidence Intervals — practice questions

Explore 2 free Confidence Intervals questions in AP Statistics Statistics. Open each question or exercise to read its content, reference answers and available explanation.

Practise Confidence Intervals with Quill →

Confidence Intervals questions and exercises with answers

Showing questions 1–2 of 2.

A sample produces x-bar = 7 with an error bound of EBM = 2.5. What is the resulting confidence interval?Read the answer and worked solution →Continuing the exam-score example, σ = 3, n = 36, x-bar = 68, and z(0.05) = 1.645 for a 90% confidence level. What is the resulting confidence interval?Read the answer and worked solution →

Worked practice questions

A sample produces x-bar = 7 with an error bound of EBM = 2.5. What is the resulting confidence interval?

  1. (2.5, 7.0)
  2. (7.0, 9.5)
  3. (4.5, 9.5)
  4. (4.5, 7.0)
Show answer and solution

Correct answer: C. (4.5, 9.5)

1. A confidence interval takes the form (x-bar - EBM, x-bar + EBM). 2. Lower bound: 7 - 2.5 = 4.5. 3. Upper bound: 7 + 2.5 = 9.5. 4. Options B and D only apply the error bound to one side of x-bar instead of both, so they are incomplete. _Source: OpenStax Introductory Statistics (CC BY 4.0), Ch 8 "Confidence Intervals", section 8.1 A Single Population Mean using the Normal Distribution_

Open this question →

Continuing the exam-score example, σ = 3, n = 36, x-bar = 68, and z(0.05) = 1.645 for a 90% confidence level. What is the resulting confidence interval?

  1. (67.18, 68.82)
  2. (65.00, 71.00)
  3. (68.00, 71.65)
  4. (64.36, 71.65)
Show answer and solution

Correct answer: A. (67.18, 68.82)

1. Compute EBM = z(σ/sqrt(n)) = (1.645)(3/sqrt(36)) = (1.645)(0.5) = 0.8225. 2. Lower bound: 68 - 0.8225 = 67.1775, which rounds to 67.18. 3. Upper bound: 68 + 0.8225 = 68.8225, which rounds to 68.82. 4. Option D doubles the error bound by mistake, giving a needlessly wide interval. _Source: OpenStax Introductory Statistics (CC BY 4.0), Ch 8 "Confidence Intervals", section 8.1 A Single Population Mean using the Normal Distribution_

Open this question →

How to practise

  1. Choose a Confidence Intervals question and try to work out your answer.
  2. Open the question to check the correct answer and read its worked solution.
  3. Continue in the app for bite-sized lessons, explanations and review with Quill. You can start without creating an account.

More Statistics topics

Sampling and DataThe F Distribution and One-Way ANOVAContinuous Random VariablesDescriptive StatisticsHypothesis TestingLinear Regression and CorrelationThe Normal DistributionProbability Topics