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Accepting/rejecting shipments via acceptance procedures
Problem 1
A company receives a shipment of 16 items. A random sample of 4 items is selected,
and the shipment is rejected if any two of these items proves to be defective.
What is the probability of accepting a shipment containing 4 defective items ?
Solution
The probability that the shipment will be is equal to the probability to find 0 or 1
defective items in the random sub-set of 4 (four) items in the set of 16 items.
The number of all possible quadruples of 16 items is = = 1820.
The number of all possible quadruples of the form (0 defective,4 good) is = 1*495 = 495.
The number of all possible quadruples of the form (1 defective,3 good) is = 4*220 = 880.
So the probability that the shipment will be accepted is
P = = = = 0.755494505 = 75.55% (rounded). ANSWER
Problem 2
A shipment of 10 items has two defective and eight non defective units.
In the inspection of the shipment, a sample of 4 (four) units will be selected and tested.
If a defective unit is found, the shipment of 10 units will be rejected.
If a random sample of four items is tested, what is the probability that the shipment will be rejected?
Solution
The probability that the shipment will be rejected is equal to the probability to find at least
one defective item in the random set of 4 (four) items.
The number of all possible quadruples of 10 items is = = 210.
The number of all possible quadruples of the form (1 defective,3 good) is = = 112.
The number of all possible quadruples of the form (2 defective,2 good) is = = 28.
So the probability that the shipment will be rejected is
P = = = . ANSWER