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Math Help - Help probability question

  1. #1
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    Help probability question

    This is probably a simple question but I can't get it
    P(A)=0.5 and P(AuB)=0.6, find P(B) if A and B are independent
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  2. #2
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    Quote Originally Posted by Happy Dancer View Post
    This is probably a simple question but I can't get it
    P(A)=0.5 and P(AuB)=0.6, find P(B) if A and B are independent
    A and B are independent so P(A \cup B)=P(A)+P(B)-P(A)B(B).
    Now solve for P(B).
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  3. #3
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    Thanks, btw I have another problem. Find P(B) given that P(A|B)=0.4
    P(B)=P(AnB)/P(A|B)=P(A)P(B)/P(A|B)
    so P(B)=1.25 P(B)
    How can this be right?
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  4. #4
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    Quote Originally Posted by Happy Dancer View Post
    Thanks, btw I have another problem. Find P(B) given that P(A|B)=0.4
    P(B)=P(AnB)/P(A|B)=P(A)P(B)/P(A|B)
    so P(B)=1.25 P(B)
    How can this be right? What you have done is not correct!
    You must have been given some information about P(A).
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  5. #5
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    Yes, carrying on from the previous question P(A)=0.5
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  6. #6
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    Quote Originally Posted by Happy Dancer View Post
    Yes, carrying on from the previous question P(A)=0.5
    If A & B are independent then P(A)=0.4 \ne 0.5!
    So there is a mistake in the problem.

    Why not post the exact question.
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