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12 August, 12:50

Suppose that only 65% of all drivers in a certain state wear a seat belt. a random sample of 80 drivers is selected. what is the probability that more than forty-two drivers wear a seat belt?

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  1. 12 August, 13:17
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    Pr (X >42) = Pr (Z > - 2.344)

    = Pr (Z< 2.344) = 0.9905

    Step-by-step explanation:

    The scenario presented can be modeled by a binomial model;

    The probability of success is, p = 0.65

    There are n = 80 independent trials

    Let X denote the number of drivers that wear a seat belt, then we are to find the probability that X is greater than 42;

    Pr (X > 42)

    In this case we can use the normal approximation to the binomial model;

    mu = n*p = 80 (0.65) = 52

    sigma^2 = n*p * (1-p) = 18.2

    Pr (X >42) = Pr (Z > - 2.344)

    = Pr (Z< 2.344) = 0.9905
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