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    • Thread Starter

    Heinmann Modular Mathematics (greg attwood, gill dyer, gordon skipworth)
    Blue Cover with Statistics 1 written on it
    Exercise 8A, pg 153, qn 15

    hi can you please help me on this qn, thanx. i would have thought that this question was just a normal simple probability question, not one to do with probability distributions.
    • Thread Starter

    ...can ANYONE help me???? please, i'm really stuck!

    i've done it...but i used a big tree diagram

    if the number tested is three, there must be one good and two bad
    use probabilities without replacement
    There are three combinations it could be - good bad bad, bad bad good, bad good bad. If you add these together you get 2/15

    For part b use the same idea
    4 ways there could be 4 picked - good good bad bad, good bad good bad, bad good good bad, good bad bad good. This gives 4/15
    Add this to above answer gives 6/15
    Or the two bad fuses could be picked, which is 1/15
    Gives a total of 7/15
    • Thread Starter

    thanx dude, u a star
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Updated: June 10, 2004
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