Company A buys large shipments of computer chips and employs this acceptance sampling plan: randomly choose and test 10 computer chips, then accept the whole batch if there is less than two defective; that is, at most one chip doesn't work. If a specific shipment of thousands of computer chips actually has a 2% rate of defects, determine the probability that this whole shipment is accepted?
Answer: P(Acceptable) = 10C0(0.02)0(0.98)10 + 10C1(0.02)1(0.98)9 = (0.98)10 + 10(0.02)(0.98)9 = 0.9838
Where did the zero come from? Why is r, the number of successes, 0?