概率题求解答（英文）A biometric security device using fingerprints erroneously refuses to admit 1 in 1,700 authorized persons from a facility containing classified information.The device will erroneously admit 1 in 1,006,000 unauthorized pe
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概率题求解答（英文）A biometric security device using fingerprints erroneously refuses to admit 1 in 1,700 authorized persons from a facility containing classified information.The device will erroneously admit 1 in 1,006,000 unauthorized pe
概率题求解答（英文）
A biometric security device using fingerprints erroneously refuses to admit 1 in 1,700 authorized persons from a facility containing classified information.The device will erroneously admit 1 in 1,006,000 unauthorized persons.Assume that 90 percent of those who seek access are authorized.
If the alarm goes off and a person is refused admission,what is the probability that the person was really authorized?
概率题求解答（英文）A biometric security device using fingerprints erroneously refuses to admit 1 in 1,700 authorized persons from a facility containing classified information.The device will erroneously admit 1 in 1,006,000 unauthorized pe
We assume that we have 100 people,and according to the question.90people are authorized,10 people are not.
And since the person we talked about it not refused,we only need to consider the people who are refused.
Based on the condition,in 100 people,we have [90X(1/1700)+10X(1-1/100600)] people who will be refused.
And the ones who are really authorized but refused are [90X(1/1700)]
As analyzed above,the probability should be [90X(1/1700)]/ [90X(1/1700)+10X(1-1/100600)]