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Math Help - 2 probability questions

  1. #1
    munkeyb0i
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    2 probability questions

    I have just recently been learning probability and I have been having troubles with some questions. If someone can help me on these two question, I would appreciate it.

    1. A basketball player has a success rate of 80% for shooting free throws. What is the probability she will make atleast three out of 5 attempts.

    2. A person is chosen at random from shoppers at a store. If the person's probability of having blonde hair and glasses is 2/25 and the probability of wearing glasses is 9/25, determine P(blonde hair|wears glasses).
    The only thing I could do is do a venn diagram for this question and I'm not too sure if it's even right. Please reply if you know how to do these two questions.

    Thanks
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by munkeyb0i

    1. A basketball player has a success rate of 80% for shooting free throws. What is the probability she will make atleast three out of 5 attempts.
    The probability of making the three shots and missing the other two is:

    \frac{5!}{3!2!}0.8^3\times 0.2^2=\frac{5.4.3.2.1}{3.2.1\times2.1 }0.8^3\times 0.2^2\approx 0.205

    This is the probability of three successes in 5 attempts for a binomially
    distributed random variable with probability of success on a single attempt of
    0.8.

    Your notes/text book should provide a detailed explanation of why this is the
    case.

    RonL
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  3. #3
    Grand Panjandrum
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    Quote Originally Posted by munkeyb0i
    2. A person is chosen at random from shoppers at a store. If the person's probability of having blonde hair and glasses is 2/25 and the probability of wearing glasses is 9/25, determine P(blonde hair|wears glasses).
    The only thing I could do is do a venn diagram for this question and I'm not too sure if it's even right.
    P(blond and glassess)=P(blong|glasses)P(glasses)

    so:

    2/25=P(blond|glasses).9/25

    hence:

    P(blond|glasses)=2/25.25/9=2/9

    RonL
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