Accuracy measures

Interpretation

How to calculate

True positive (TP)

Mineral correctly identified as present on the map

a

False positive (FP)

Non-mineral incorrectly identified as present on the map

b

True negative (TN)

Non-mineral correctly identified as absent on the map

d

False negative (FN)

Mineral incorrectly identified as absent on the map

c

Sensitivity

Conditional probability that a true “present” is correctly classified on the map

TP/(TP + FN) = a/(a + b)

Specificity

Conditional probability that true “absent” is correctly classified on the map

TN/(TN + FP) = d/(b + d)