Question 517983: I am having trouble about applying my knowldege of permutations and combinations
Here is a problem: From a shipment of 35 transistors, 5 of which are defective, a sample of 8 transistors is selected at random.
How many samples contain exactly 3 defective transistors?
How many samples contain no defective transistors?
How many samples contain at least 4 defective transistors?
I tried doing combinations like 35 C 3, but that does not give the right answer. any direction or general rules that can be applied to further problems would be much appreciated!
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! From a shipment of 35 transistors, 5 of which are defective, a sample of 8 transistors is selected at random.
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Binomial Problem with n = 8 and p(defect) = 1/7 ; p(no defect) = 6/7
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How many samples contain exactly 3 defective transistors?
P(x = 3) = 8C3(1/7)^3(6/7)^5 = 0.0755
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How many samples contain no defective transistors?
P(x = 0) = (6/7)^8 = 0.2914
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How many samples contain at least 4 defective transistors?
P(4<= x <= 8) = 1 - P(0<= x <=3) = 0.0180
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Cheers,
Stan H.
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