AP Statistics · Topic 4.4

Mutually Exclusive Events Practice

Part of Probability, Random Variables, and Probability Distributions.(VAR-4.B)

Practice questions

4

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Sample questions

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  1. Sample 1difficulty 2/5

    For mutually exclusive A, B: P(A or B) =

    • A

      1 − P(A)P(B)

    • B

      P(A) · P(B)

    • C

      P(A) + P(B) − P(A∩B)

    • D

      P(A) + P(B)

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    Why

    Mutually exclusive ⇒ P(A∩B) = 0.

  2. Sample 2difficulty 2/5

    Events A and B are mutually exclusive with P(A) = 0.30 and P(B) = 0.25.

    A: 0.3 B: 0.25

    What is P(A or B)?

    • A

      0.05

    • B

      0.30

    • C

      0.075

    • D

      0.55

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    Why

    Mutually exclusive: P(A and B) = 0. So P(A or B) = 0.30 + 0.25 = 0.55.

  3. Sample 3difficulty 3/5

    For 3 mutually exclusive events with probabilities 0.2, 0.3, 0.4, P(none) =

    • A

      0.2

    • B

      0.5

    • C

      0.1

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    • D

      0.9

    Why

    P(any) = 0.9; P(none) = 1 − 0.9 = 0.1.

  4. Sample 4difficulty 3/5

    Two events A and B both have positive probability and are mutually exclusive.

    Which statement must be true?

    • A

      P(A and B) = P(A)P(B)

    • B

      P(A) + P(B) = 1

    • C

      A and B cannot be independent

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    • D

      A and B must be independent

    Why

    If mutually exclusive with positive probabilities, P(A and B) = 0 but P(A)P(B) > 0, so they cannot be independent.