Specificity

The proportion of individuals without a condition who are correctly identified as such by a test. It is calculated thus: Specificity = TN/(TN+FP), where TN is the number of true negatives and FP is the number of false positives. The terms 'positive' and 'negative' are used to refer to the presence or absence of the condition of interest. In the figure, specificity = d/(b + d). Cf. Negative Predictive Value, Positive Predictive Value, Sensitivity.

Diagnosis Present Absent

"S

OJ

a

b

OJ

(true positive)

(false positive)

PL,

OJ

c

d

tA

(false negative)

(true negative)

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