Table 3.

Statistical variables of the performance of a binary classification test

Acronym	Full name	Definition/Formula
TP	True positive	Toxic compounds predicted as toxic
TN	True negative	Non toxic compounds predicted as non toxic
FP	False positive	Non toxic compounds predicted as toxic
FN	False negative	Toxic compounds predicted as non toxic
FP%	False positive rate	Ratio of non toxic compounds incorrectly classified as toxic FP/(FP + TN)
FN%	False negative rate	Ratio of toxic compounds incorrectly classified as non toxic FN/(FN + TP)
Sensitivity	Sensitivity or true positive rate	Ratio of toxic compounds correctly classified as toxic TP/(TP + FN)
Specificity	Specificity or true negative rate	Ratio of non toxic compounds correctly classified as non toxic TN/(FP + TN)
Accuracy	Accuracy or concordance	Proportion of the total number of predictions that were correct (TP + TN)/(TP + TN + FP + FN)
PPV	Positive predictive value	Ratio of the predicted toxic compounds that were correct TP/(TP + FP)
NPV	Negative predictive value	Ratio of the predicted non toxic compounds that were correct TN/(TN + FN)