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Math Help - probability >>>> my solution truth or not??

  1. #1
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    probability >>>> my solution truth or not??

    a box contain :

    7white
    3red
    4black
    and 6 green balls
    if we choose 8 balls randomly without replacement . if selecting a white or a black ball is consider as wining >>>find :

    (1) the probability that we get 6 wining balls
    (2) the expected value for number of wining

    my solutions:
    (1)f(x)=
    (11C6)*(9C2)\(20C8)
    C: means combination

    (2)
    mean = 88\20
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  2. #2
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    Quote Originally Posted by flower3 View Post
    a box contain :

    7white
    3red
    4black
    and 6 green balls
    if we choose 8 balls randomly without replacement . if selecting a white or a black ball is consider as wining >>>find :

    (1) the probability that we get 6 wining balls
    (2) the expected value for number of wining

    my solutions:
    (1)f(x)=
    (11C6)*(9C2)\(20C8)
    C: means combination Mr F says: Correct.

    (2)
    mean = 88\20 Mr F says: Correct.
    And you realise that the number of successful balls drawn follows a hypergeometric distribution?
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  3. #3
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    And you realise that the number of successful balls drawn follows a hypergeometric distribution?
    yes i know that because i use the law of mean for a hypergeometric distribution :

    mu = nr\N

    n:#of balls drawn
    r: # of total success=the balls that make us wining
    N: # of total balls

    mu = nr\N

    =(11*8) \ 20
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