Question 1131142: Printed circuit cards are placed in a functional test after being populated with semiconductor chips. A lot contains 21 cards, and 4 are selected without replacement for functional testing.
(Pleaee enter your answers as fractions in lowest terms or as decimals rounded to four decimal places. Thank you!)
a. If 15 cards are defective, what is the probability that at least one defective card is in the sample?
b. If 14 cards are defective, what is the probability that at least one defective card is in the sample?
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! The easiest way to do this is find probability no defective cards are chosen and subtract that from one
(6/21)*(5/20)*(4/19)*(3/18)=0.0025, so answer is 1-0.0025 =0.9975
For 14, (7/21)(6/20(5/19)(4/14)=0.0058, so answer is 0.9942.
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