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Math Help - Bayes’ Theorem- confusion

  1. #1
    Junior Member
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    Bayes’ Theorem- confusion

    ive been reading a bit about bayes theorem and the answer to this question has me confused


    question:
    Two video products distributors supply video tape boxes to
    a video production company. Company A sold 100 boxes of which 5 were
    defective. Company B sold 300 boxes of which 21 were defective. If a box
    was defective, .find the probability that it came from Company B.

    The answer given is
    0
    :192

    has the author of the question calculated that the defective box came from
    company A not company b

    so the answer should be 0.8076
    or have i missed something here?

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  2. #2
    MHF Contributor
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    Bayes' is basically pointing out that you can rearrange...




    Hopefully you can see why it's 5/26


    Edit: wow, misread it myself and did A... yes, you're right!

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  3. #3
    Member rtblue's Avatar
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    The number of non defective items does not matter. We are given that a defective item is found. There are only 26 defective items in circulation, 21 of which came from B. Therefore, the probability of the defective item coming from B is 21/26, which is 0.8076
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