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Math Help - sensitivity/specificity problem

  1. #1
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    sensitivity/specificity problem

    A test has 60% sensitivity and 20% false positive rate. The test on a patient is negative. What is the probability that the test is a false negative?

    How do I set up this problem to solve?

    Thank you!
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  2. #2
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    Re: sensitivity/specificity problem

    I think I understand "20% false negative" but what does "60% sensitivity" mean? That in 40% of the tests, it will not give a definite answer?
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  3. #3
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    Re: sensitivity/specificity problem

    60% sensitivity= true positives/true positives + false negatives

    20% false positive

    I was thinking that if you have 20% false positive then you would have 80% true positive, so to solve for false negative:

    sensitivity (60%)= true positive (80%)/true positive (80%) + X (false negatives)

    I don't think I'm setting this up right because when I solve for X I get a negative number. So I either set it up wrong or I don't remember algebra or both

    Thank you for your help!
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