AP Statistics · Topic 6.6

Concluding a Test for a Population Proportion Practice

Part of Inference for Categorical Data: Proportions.(VAR-6.D)

Practice questions

4

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Sample questions

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  1. Sample 1difficulty 2/5

    Test H₀: p = 0.25 vs Hₐ: p ≠ 0.25, with n=400, p̂ = 0.30.

    SE₀ = sqrt(0.25·0.75/400) = 0.02165 z = (0.30 − 0.25)/0.02165

    The test statistic is approximately:

    • A

      2.31

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    • B

      1.96

    • C

      1.15

    • D

      0.05

    Why

    z ≈ 0.05/0.02165 ≈ 2.31.

  2. Sample 2difficulty 2/5

    A test of H₀: p = 0.4 vs Hₐ: p ≠ 0.4 yields p-value = 0.08 with α = 0.05.

    p-value = 0.08, α = 0.05

    Which conclusion is appropriate?

    • A

      Accept H₀; p equals 0.4.

    • B

      Fail to reject H₀; insufficient evidence that p ≠ 0.4.

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    • C

      Cannot determine without more data.

    • D

      Reject H₀; convincing evidence that p ≠ 0.4.

    Why

    Since 0.08 > 0.05, fail to reject H₀. There is not convincing evidence that p ≠ 0.4.

  3. Sample 3difficulty 2/5

    A z-test of H₀: p = 0.5 vs Hₐ: p > 0.5 produces p-value = 0.012. Significance level α = 0.05.

    p = 0.012

    What is the correct decision and conclusion?

    • A

      Accept H₀; the proportion equals 0.5.

    • B

      Reject H₀; there is convincing evidence p > 0.5.

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    • C

      Reject Hₐ; the data support H₀.

    • D

      Fail to reject H₀; not enough evidence.

    Why

    Since p-value (0.012) < α (0.05), reject H₀. There is convincing evidence that p > 0.5.

  4. Sample 4difficulty 3/5

    Output for a one-proportion z-test of H₀: p = 0.50 vs Hₐ: p > 0.50.

    1-PropZTest prop > 0.5 z = 2.20 p = 0.0139 p̂ = 0.555 n = 400

    At α = 0.05, the conclusion is:

    • A

      Accept H₀.

    • B

      Fail to reject H₀.

    • C

      Insufficient data.

    • D

      Reject H₀; convincing evidence p > 0.50.

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    Why

    P-value 0.0139 < 0.05, so reject H₀; there is convincing evidence p > 0.50.