SOLUTION: I am not even sure where to start with this problem. Any assistance would be helpful. Thank you! A survey of 12 people at a bookstore showed that five had purchased a hardcover

Question 133741: I am not even sure where to start with this problem. Any assistance would be helpful. Thank you!
A survey of 12 people at a bookstore showed that five had purchased a hardcover book. If seven people are selected at random, what is the probability that four of them had purchased a hardcover book?
Answer by stanbon(48568) (Show Source):
You can put this solution on YOUR website!
A survey of 12 people at a bookstore showed that five had purchased a hardcover book. If seven people are selected at random, what is the probability that four of them had purchased a hardcover book?
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From the survey you have P(person buys a hardcover book) = 5/12
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In a random sample of 7 you have a binomial problem with p = 5/12
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P(4 buy out of 7) = 7C4(5/12)^4(7/12)^3 = 0.2094
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If you have a TI calculator that is binompdf(7,(5/12),4)
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Cheers,
Stan H.