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Math Help - probability problem

  1. #1
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    probability problem

    Mr. Johnson gives his class a list of 20 study questions from which he will select 8 to be answered on the final exam. If a student knows how to answer 14 of the 20 questions, what is the probability the student will be able to answer correctly:
    a) all 8 questions
    b) exactly 5 questions
    c) at least 6 questions

    explain your reasoning please
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by rutheada000 View Post
    Mr. Johnson gives his class a list of 20 study questions from which he will select 8 to be answered on the final exam. If a student knows how to answer 14 of the 20 questions, what is the probability the student will be able to answer correctly:
    a) all 8 questions
    b) exactly 5 questions
    c) at least 6 questions

    explain your reasoning please
    use Bernoulli Trials (the binomial distribution) with n = 8 and p = 14/20 = 7/10
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  3. #3
    Eater of Worlds
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    You can use a binomial probability.

    For the second one, p=14/20=.70, q=1-p, k=5, n=8

    C(n,k)p^{k}q^{n-k}

    C(8,5)(0.7)^{5}(0.3)^{3}

    You can adjust accordingly on the others.
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