In: Statistics and Probability
A box of manufactured items contains 12 items of which 4 are defective. If 3 items are drawn at random without replacement, what is the probability that:
1. The first one is defective and rest are good
2. Exactly one of three is defective
Out of 12 items, 4 are defective and 8 are good.
1:
Since draws are done without replacement so after first defective we have 8 good items out of 11 items. Likewise after second good item, we have 7 good items out of 10 items. So the probability that the first one is defective and rest are good is
P(the first one is defective and rest are good) = (4/12) * (8/11) * (7/10) = 0.1697
2:
Here we need to use hypergeometric distribution. The probability that exactly one of three is defective is