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Math Help - probability #2

  1. #1
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    probability #2

    another one..

    25% of all students at the high school wears glasses. you randomly chose 15 students. what is the possibility that 7 or more of these students wears glasses?
    Last edited by mr fantastic; December 9th 2009 at 05:45 AM. Reason: Edited post title
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  2. #2
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    You should consider the binomial theorem

    Where n is number of trials, p is the probabilty of success and k is the required amount.

     P(X=k) = \binom{n}{k}p^k(1-p)^{n-k}

    In your case n = 15 and p = 0.25

    Choose k \geq 7

    P(X\geq 7) = P(X= 7)+P(X= 8)+\dots +P(X= 14)+P(X= 15)
    Last edited by mr fantastic; December 9th 2009 at 05:43 AM. Reason: Removed quote tag
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  3. #3
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    Quote Originally Posted by pickslides View Post
    You should consider the binomial theorem

    Where n is number of trials, p is the probabilty of success and k is the required amount.

     P(X=k) = \binom{n}{k}p^k(1-p)^{n-k}

    In your case n = 15 and p = 0.25

    Choose k \geq 7

    P(X\geq 7) = P(X= 7)+P(X= 8)+\dots +P(X= 14)+P(X= 15)
    This will be true as long as the number of students at the Highschool is 'large'.
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