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AP Statistics / Unit 3

Unit 3 · 15–25%

Inference for Categorical Data: Proportions

Use sample proportions to estimate or test a population proportion.

Start first lessonUnit practice

Topics

  • Sampling distributions for a proportion
  • Confidence intervals for one proportion
  • Significance tests for one proportion
  • Comparing two proportions
  • Type I and Type II errors

Lessons

Key terms

Original practice

Marlow Works questions. If this unit does not have its own items yet, you will see other questions from the same course.

1 of 1Inference for Categorical Data: Proportions · hard · free response

A simple random sample of 400 city voters finds that 0.47 support a transit tax. A 95% confidence interval is 0.47 ± 0.049. Explain what this interval means, state one thing it does not mean, and say whether a similar sample of size 100 would tend to produce a wider or narrower interval.

Original Marlow Works item — not a College Board question.

Take your time—this is practice, not a test.

Review checklist

  1. 01Identify the parameter in words before computing.
  2. 02Check randomness, independence, and success-failure conditions.
  3. 03Write interval and test conclusions in context, not only in symbols.

Related resources

External links with reuse status. Marlow Works is independent and does not copy restricted exam or textbook material.

  • Official / link only

    AP Statistics course page

    Official revised 2026–27 five-unit framework.

    College Board · All rights reserved · accessed 2026-10-01

    Open source

  • CC BY — attribution required

    Collaborative Statistics

    Open statistics text for distributions, probability, and inference.

    Open Textbook Library listing · CC BY · accessed 2026-10-01

    Open source