A shipment of 80 alarms contains four that are defective. If three from the shipment are randomly selected and shipped to a customer, find
a) the probability that the customer will get exactly 1 bad unit,
b) the probability that the cutsomer will get exactly 1 bad unit using the binomial distribution as an approximation.
Binomial distribution
2007-09-20 5:23 am
回答 (1)
2007-09-20 7:43 pm
✔ 最佳答案
a. using method of counting, the prob.:(4 C 1 x 76 C 2 ) / 80 C 3
= 0.1388 (4 sign fig)
b. using binomial distribution, we have to find out prob. of picking a bad unit first:
( 4 / 80 )
= 1/20
The required prob.
3 C 1 x (1/20) x (19/20)^2
=0.1354 (4 sign fig)
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