Question 561912: In a scientific study there are 12 guinea pigs, 5 of which are pregnant. If 3 are selected at random without replacement, find the probability that none are pregnant. Enter your answer as a fraction.
I can find the probability that all are pregnant but I cant seem to be able to solve this problem. I would really appreciate if someone can guide me step by step how to solve it. Thank you, in advance =]
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! In a scientific study there are 12 guinea pigs, 5 of which are pregnant. If 3 are selected at random without replacement, find the probability that none are pregnant. Enter your answer as a fraction.
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Binomial Problem with n = 3 and p(not pregnant) = 7/12
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P(x = 0) = 3C3*(7/12)^3*(5/12)^0 = (7/12)^3 = 0.1985
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Cheers,
Stan H.
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