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Math Help - Probability Help

  1. #1
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    Probability Help

    Hello, I know this is probably simple but i just cant find out how to get the correct answer.

    When P(A and B and C), How do i find just P(A and C) and also just P(B and C)?

    Is there a formula to follow like the multiplication rule? I'm stumped.
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  2. #2
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    Just brainstorming.

    Only when events A, B and C are all independent of each other you can use the multiplication rule, thus having P(A\cap B\cap C)=P(A)P(B)P(C). Otherwise you have use conditional probability which states that P(A|B)=\frac{P(A\cap B)}{P(B)}. From there you can write P(A\cap B)=P(A|B)P(B).

    So you could write P(A\cap B \cap C)=P(A|B\cap C)P(B\cap C)=P(A|B\cap C)P(B|C)P(C).

    See if this will get you started.
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