AP Statistics · Topic 2.2

Representing Two Categorical Variables Practice

Part of Exploring Two-Variable Data.(UNC-1.H)

Practice questions

17

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Sample questions

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  1. Sample 1difficulty 1/5

    The two-way table shows pet ownership by grade.

    Pet ownership by grade Grade Pet No Pet Total 9 40 20 60 10 30 30 60 Total 70 50 120

    What is the marginal proportion of students who own a pet?

    • A

      40/60

    • B

      40/120

    • C

      70/120

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    • D

      70/60

    Why

    The marginal proportion uses the row/column total over the grand total: 70 owners out of 120 students.

  2. Sample 2difficulty 1/5

    The table shows music preference vs whether students play a sport.

    Music vs Sport preferences Music Yes No Total Pop 35 15 50 Rock 25 25 50 Total 60 40 100

    What is the marginal proportion of Pop fans?

    • A

      35/50 = 0.70

    • B

      15/40 = 0.375

    • C

      35/60 = 0.58

    • D

      50/100 = 0.50

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    Why

    Marginal proportion uses the row total over the grand total: 50/100 = 0.50.

  3. Sample 3difficulty 2/5

    The table cross-classifies allergy by exposure.

    Allergy by exposure Exposure Allergy None Total Yes 45 155 200 No 15 285 300 Total 60 440 500

    Among those with allergies, what proportion was exposed?

    • A

      60/500 = 0.12

    • B

      200/500 = 0.40

    • C

      45/60 = 0.75

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    • D

      45/200 = 0.225

    Why

    Conditioning on Allergy = Yes column total of 60: 45 of 60 had exposure, giving 0.75.

  4. Sample 4difficulty 2/5

    A two-way table is used for

    • A

      Two categorical variables

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    • B

      Time series

    • C

      One categorical variable

    • D

      One quantitative variable

    Why

    Cells display joint counts of categories from two categorical variables.

  5. Sample 5difficulty 2/5

    Bars show conditional percentage of "Yes" in three groups.

    Group % Yes A B C

    Which conclusion is supported?

    • A

      Group is independent of response

    • B

      Group sizes are equal

    • C

      The Yes-rate depends on group; B has the highest, C the lowest

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    • D

      All groups have equal Yes-rates

    Why

    The differing bar heights show different conditional proportions, indicating an association.