Question 199456
A population consists of 15 items, 10 of which are acceptable. In a sample of 4 items, what is the probability that exactly three are acceptable? Assume the samples are drawn without replacement.
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# of ways to pick 3 "acceptable": 10C3 = 120
# of ways to pick 1 not acceptable: 5C1 = 5
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# of ways to pick 4 where exactly 3 are acceptable: 120*5 = 600
# of ways to pick 4 with no restrictions: 15C4 = 1365
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Probability that you want = 600/1365 = 40/91
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Cheers,
Stan H.