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Math Help - Combinatorics

  1. #1
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    Combinatorics

    We have a bowl, inside of which are 6 balls.

    5 of them are black. 1 of them is white.


    We pull out 1 ball from the basket. Then we return the ball to the basket.

    We repeat this 8 times.




    What is the probability we pulled out a black ball precisley 4 times and pulled out a white ball precisley 4 times?


    Thanks
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  2. #2
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    Quote Originally Posted by user_name View Post
    We have a bowl, inside of which are 6 balls. 5 of them are black. 1 of them is white. We pull out 1 ball from the basket. Then we return the ball to the basket. We repeat this 8 times.
    What is the probability we pulled out a black ball precisely 4 times and pulled out a white ball precisley 4 times?
    Because the drawn ball is returned, it is the same on every draw. Therefore the events are independent and are modeled by binominal distribution. Then p= 1/6 & N=8. So C(8,4)[(1/6)^4][(5/6)^4].
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  3. #3
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    Ah, binominal!

    I knew I was missing something fairly obvious, but couldn`t figure out what.

    Cheers, mate.
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