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    I'm really stuck on this question.

    An archer hits the bullseye with a probability 0.6. She shoots 20 arrows at a time.
    a) Find the probability that she hits with at least 50% of her arrows. She shoots 12 sets of 20 arrows.
    b) Find the probability that she hits with at least 50% of her arrows in 7 of the 12 sets of arrows.
    c) Find the probability that she hits with at least 50% of her arrows in fewer than 6 sets of arrows

    I've done similar questions before with my calculator but this is more complicated. The book says the answers (a- 0.8725 b- 0.01027 c-0.0002407) but i have no idea how to get there.

    Any help is appreciated
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    (Original post by BusinessPug)
    I'm really stuck on this question.

    An archer hits the bullseye with a probability 0.6. She shoots 20 arrows at a time.
    a) Find the probability that she hits with at least 50% of her arrows. She shoots 12 sets of 20 arrows.
    b) Find the probability that she hits with at least 50% of her arrows in 7 of the 12 sets of arrows.
    c) Find the probability that she hits with at least 50% of her arrows in fewer than 6 sets of arrows

    I've done similar questions before with my calculator but this is more complicated. The book says the answers (a- 0.8725 b- 0.01027 c-0.0002407) but i have no idea how to get there.

    Any help is appreciated

    So you can define the question using a binomial distribution: X ~ B(20, 0.6)
    This should help you get started for part (a)
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    (Original post by Caecilius_)
    So you can define the question using a binomial distribution: X ~ B(20, 0.6)
    This should help you get started for part (a)
    I've tried doing that but it doesn't give me the correct answer.
    I tried a few ways. I tried that with 10 as X and then with 120 as X and 240 as N
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    (Original post by BusinessPug)
    I've tried doing that but it doesn't give me the correct answer.
    I tried a few ways. I tried that with 10 as X and then with 120 as X and 240 as N
    Using X ~ B(20, 0.6),

    Doing P(X>= 10) gives 0.8725.

    Remember that P(X>= 10) = 1 - P(X<=9)
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    (Original post by caecilius_)
    using x ~ b(20, 0.6),

    doing p(x>= 10) gives 0.8725.

    Remember that p(x>= 10) = 1 - p(x<=9)
    Thank you, it was so obvious and i couldn't see it
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    (Original post by BusinessPug)
    I'm really stuck on this question.

    An archer hits the bullseye with a probability 0.6. She shoots 20 arrows at a time.
    a) Find the probability that she hits with at least 50% of her arrows. She shoots 12 sets of 20 arrows.
    b) Find the probability that she hits with at least 50% of her arrows in 7 of the 12 sets of arrows.
    c) Find the probability that she hits with at least 50% of her arrows in fewer than 6 sets of arrows

    I've done similar questions before with my calculator but this is more complicated. The book says the answers (a- 0.8725 b- 0.01027 c-0.0002407) but i have no idea how to get there.

    Any help is appreciated
    Also, the "She shoots 12 sets of 20 arrows." is for part (b) right?
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    (Original post by BusinessPug)
    Thank you, it was so obvious and i couldn'tt see it
    no problem
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    (Original post by Caecilius_)
    Also, the "She shoots 12 sets of 20 arrows." is for part (b) right?
    I'm not sure cause I didn't get that far :ahee:
 
 
 
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