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. Author manuscript; available in PMC: 2020 Jul 1.
Published in final edited form as: Addict Behav. 2018 Nov 22;94:50–56. doi: 10.1016/j.addbeh.2018.11.029

Table 1.

Definition of the Diagnostic Accuracy Indices

Mathematical Definition Meaning
Proportion Selected
(Diagnosed)		 PSk = p(Ak) + p(Bk) Proportion of individuals being
Positively diagnosed; prevalence
rates based on the criteria
Success Ratio SRk = p(Ak) / [p(Ak) + p(Bk)] Proportion of individuals who are
truly positive among all
individuals being positively
diagnosed by the diagnostic
criteria
Sensitivity SEk = p(Ak) / [p(Ak) + p(Dk)] Proportion of individuals who are
correctly positively diagnosed by
the diagnostic criteria among all
individuals who truly are positive
Specificity SPk = p(Ck) / [p(Ck) + p(Bk)] Proportion of individuals who are
correctly ruled out by the
diagnostic criteria among all
individuals who are negative

Note: A = true positive, B = false positive, C = true negative, D = false negative, and p(·) represents the probability of a particular possibility. The index k denotes the population, where k = r represents the reference population and k = f represents the focal population.