AP Statistics · Topic 6.9

Justifying a Claim About the Difference of Two Proportions Practice

Part of Inference for Categorical Data: Proportions.(UNC-4.D)

Practice questions

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Sample questions

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  1. Sample 1difficulty 3/5

    A 95% CI for p_A − p_B is (0.05, 0.20).

    0 0.05 0.20

    What can we conclude?

    • A

      p_A and p_B differ by exactly 0.125.

    • B

      No difference between groups.

    • C

      Convincing evidence p_A < p_B.

    • D

      Convincing evidence p_A > p_B (since 0 is not in the CI).

      check_circle

    Why

    Both endpoints positive and 0 excluded, so we have evidence p_A > p_B.

  2. Sample 2difficulty 3/5

    A 95% CI for p_A − p_B is (−0.02, 0.10).

    0 −0.02 0.10

    What does the interval suggest about the difference in proportions?

    • A

      There is convincing evidence p_A < p_B.

    • B

      The proportions must be equal.

    • C

      Since 0 is in the interval, no convincing evidence of a difference.

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    • D

      There is convincing evidence p_A > p_B.

    Why

    A two-sample CI for the difference that contains 0 means we cannot conclude the proportions differ.