AP Statistics · Topic 8.6

Carrying Out a Chi-Square Test for Homogeneity or Independence Practice

Part of Inference for Categorical Data: Chi-Square.(VAR-8.E)

Practice questions

11

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Sample questions

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  1. Sample 1difficulty 2/5

    A chi-square test of independence yields chi-square = 9.21 with 4 degrees of freedom.

    Chi-Square Distribution, df=4 9.21 p-value

    Which best describes the p-value?

    • A

      P(chi-square >= 9.21 | df=4)

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    • B

      P(chi-square <= 9.21 | df=4)

    • C

      P(chi-square = 9.21 | df=4)

    • D

      P(chi-square > 9.21 | df=5)

    Why

    The p-value for a chi-square test is the probability of observing a chi-square statistic at least as extreme (i.e., as large or larger) as the observed value, under the null hypothesis.

  2. Sample 2difficulty 2/5

    A chi-square test of independence with df = 6 produces chi-square = 14.5 and p-value = 0.024. Use alpha = 0.05.

    df=6, chi-sq=14.5, p=0.024 14.5

    What is the correct conclusion?

    • A

      Reject H0; there is significant evidence of an association

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    • B

      Accept H0; the variables are independent

    • C

      Reject H0; the variables are independent

    • D

      Fail to reject H0; no evidence of association

    Why

    Since p-value (0.024) < alpha (0.05), reject H0. There is significant evidence of an association between the two variables.

  3. Sample 3difficulty 2/5

    Software reports: chi-square = 8.40, df = 4, p = 0.078.

    Output chi-square = 8.40 df = 4 p-value = 0.078

    At alpha = 0.05, conclusion?

    • A

      Fail to reject H0; insufficient evidence of association

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    • B

      Reject H0

    • C

      p too low to interpret

    • D

      Accept H0

    Why

    Since p = 0.078 > alpha = 0.05, fail to reject H0. There is insufficient evidence of association.

  4. Sample 4difficulty 3/5

    A complete report includes

    • A

      Just the conclusion

    • B

      Test name, hypotheses, conditions, χ², df, p-value, and conclusion in context

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    • C

      Just χ²

    • D

      Just the p-value

    Why

    Full inference report is required.

  5. Sample 5difficulty 3/5

    A chi-square test of independence between music preference and age yields p = 0.31.

    Music vs Age p = 0.31

    What is the appropriate conclusion?

    • A

      p is too small to conclude anything

    • B

      Insufficient evidence to conclude music preference and age are associated

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    • C

      Music preference and age are independent

    • D

      Reject the null hypothesis

    Why

    With p = 0.31 > 0.05, fail to reject H0. We cannot conclude there is an association; this does NOT prove independence.