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Twenty percent of all telephones of a certain type are
Chapter 4, Problem 55E(choose chapter or problem)
Twenty percent of all telephones of a certain type are submitted for service while under warranty. Of these, 60% can be repaired, whereas the other 40% must be replaced with new units. If a company purchases ten of these telephones, what is the probability that exactly two will end up being replaced under warranty?
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QUESTION:
Twenty percent of all telephones of a certain type are submitted for service while under warranty. Of these, 60% can be repaired, whereas the other 40% must be replaced with new units. If a company purchases ten of these telephones, what is the probability that exactly two will end up being replaced under warranty?
ANSWER:Answer : Step 1 : Given twenty percent of all telephones of a certain type are submitted for service while under warranty. Of these, 60% can be repaired, whereas the other 40% must be replaced with new units. Let X be the number of phones submitted for service and Let R be be the number of telephones which are replaced after being submitted for service. We have the following distributions: X ~ Binomial (n = 10,p = 0.20)and X ~ Binomial (n = X,p = 0.40) x x x r Use the law of total probability to find the answer. Note that the first two probabilities in the sum are both zero, i.e., it is not possible to have. R=2 if x