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    psfrag26's Avatar
    psfrag26 Posts: 2, Reputation: 1
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    #1

    Feb 27, 2010, 11:31 PM
    probability help
    A biometric security device using fingerprints erroneously refuses to admit 1 in 1,000 authorized persons from a facility containing classified information. The device will erroneously admit 1 in 1,000,000 unauthorized persons. Assume that 95 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?
    leifweaver's Avatar
    leifweaver Posts: 39, Reputation: 11
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    #2

    Feb 27, 2010, 11:56 PM

    Out of x persons, 95% are authorized. 1/1000 are refused.
    Out of x persons, 5% are unauthorized. 999,999/1,000,000 are refused.

    So: (x*.95*1/1000)/(x*.05*999,999)=.00095/.0499995=.019
    So there is a 1.9% chance that the person was really authorized.
    Jokeveenstra's Avatar
    Jokeveenstra Posts: 1, Reputation: 1
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    #3

    Sep 23, 2012, 12:24 PM
    A biometric security device using fingerprints erroneously refuses to admit 1 in 1,800 authorized persons from a facility containing classified information. The device will erroneously admit 1 in 1,018,000 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?

    Does anyone knows the answer to this?
    paraclete's Avatar
    paraclete Posts: 2,706, Reputation: 173
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    #4

    Sep 24, 2012, 06:38 PM
    What does this to do with economics?
    dypzty's Avatar
    dypzty Posts: 1, Reputation: 1
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    #5

    Sep 23, 2013, 09:48 AM
    A biometric security device using fingerprints erroneously refuses to admit 1 in 1,000 authorized persons from a facility containing classified information. The device will erroneously admit 1 in 1,000,000 unauthorized persons. Assume that 95 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?
    pready's Avatar
    pready Posts: 3,197, Reputation: 207
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    #6

    Sep 23, 2013, 02:24 PM
    See the post above by leifweaver.
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