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A measure of the strength of a diagnostic test to distinguish between persons who do or do not have a target condition.
Note 1: A positive likelihood ratio compares the probability of a positive test result in persons with the disease with the probability of a positive test result in persons without the disease. A negative likelihood ratio compares the probability of a negative test result in persons without the disease with the probability of a negative test result in persons with the disease.
Note 2: Positive likelihood ratios greater than 10 or negative likelihood ratios less than 0.1 are sometimes judged to provide convincing diagnostic evidence.
Note 3: A positive likelihood ratio is calculated as: sensitivity ÷ (1 minus specificity). A negative likelihood ratio is calculated as: (1 minus sensitivity) ÷ specificity.
Note 4: In statistics, an alternative meaning of the likelihood ratio exists. It is the ratio of the values of the likelihood function at two different parameter values or under two different data models. See also likelihood ratio test.