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Probability: Independent vs. Dependent events

  1. Sep 19, 2011 #1
    1. The problem statement, all variables and given/known data

    2. Let a random experiment be the cast one “six-sided” die and one “four-sided” die.

    (a) Give an example of two independent events and justify your answer.
    (b) Give an example of two dependent events from this sample space and justify your answer.

    2. Relevant equations

    Independent event:
    P(A ∩ B) = P(A) * P(B|A) = P(A) * P(B)

    Dependent event:

    Not Independent, i.e. P(A) * P(B) = P(A ∩ B)

    3. The attempt at a solution

    A = {(1,1), (1,2)}

    B = {(1,1), (2,1)}

    P(B) = P(B|A) = P(A ∩ B)/P(A) = (1/24)/(2/24) = 1/2

    P(B) is not equal to 1/2
  2. jcsd
  3. Sep 20, 2011 #2


    Staff: Mentor

    No one has replied, possibly because your work is so terse, making it difficult to understand.

    Are A and B the two events? What do they represent (in words)?

    On one line you say that P(B) = 1/2, and on the next line you say that P(B) is not equal to 1/2. How can a given probability be equal to and also not equal to the same number?
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