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Math Help - probability problem

  1. #1
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    probability problem

    a doctor may confer with a someone by phone and simply call the pharmacy for medicine. suppose parents are correct ninety percent of the time and fifty families with a child are suffering from some minor sickness are selected at random.

    must find the mean variance and standard deviation of the number of parents who can identify their childs sickness.
    ~confused as to finding the number of parents, variables are confusing me.

    then need to find the probability of at least fourty two parents who are correct.

    and probability that between fourty two and fourty seven inclusive parents are correct. ~not sure how to set this one up either.

    suppose there are fourty one parents that are actually correct, would there be any evidence to suggest the claim of ninety percent of the parents being correct is false?
    ~do i use words to explain this part or is a mathematical explanation much more necessary?

    thanks.
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  2. #2
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    Quote Originally Posted by rcmango View Post
    a doctor may confer with a someone by phone and simply call the pharmacy for medicine. suppose parents are correct ninety percent of the time and fifty families with a child are suffering from some minor sickness are selected at random.

    must find the mean variance and standard deviation of the number of parents who can identify their childs sickness.
    ~confused as to finding the number of parents, variables are confusing me.

    then need to find the probability of at least fourty two parents who are correct.

    and probability that between fourty two and fourty seven inclusive parents are correct. ~not sure how to set this one up either.

    suppose there are fourty one parents that are actually correct, would there be any evidence to suggest the claim of ninety percent of the parents being correct is false?
    ~do i use words to explain this part or is a mathematical explanation much more necessary?

    thanks.
    Let X be the random variable number of parents who can identify their childs sickness.

    X ~ Binomial(n = 50, p = 0.9).
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