TABLE 4.

Summary of dogs alert versus gas chromatography-mass spectrometry (GC-MS) responses

	Dogs alerted (positive) TP	Dogs not alerted (negative) TN
Positive by GC-MS	9 (TP)	2 (FP)
Negative by GC-MS	6 (FN)	7 (TN)
Sensitivity	0.60	TPR=TP/(TP+FN)
Specificity	0.78	SPC=TN/(FP+TN)
Precision	0.82	PPV=TP/(TP+FP)
Negative predictive value	0.54	NPV=TN/(TN+FN)
False positive rate	0.22	FPR=FP/(FP+TN)
False discovery rate	0.18	FDR=FP/(FP+TP)
False negative rate	0.40	FNR=FN/(FN+TP)
Accuracy	0.68	ACC=(TP+TN)/(P+N)
F1 score	0.69	F1=2TP/(2TP+FP+FN)
Matthew's correlation coefficient	0.37	TP*TN − FP*FN/sqrt((TP+FP)×(TP+FN)×(TN+FP)×(TN+FN))

TP: true positive; TN: true negative; FP: false positive; FN: false negative; TPR: TP rate; SPC: specificity; PPV: positive predictive value; NPV: negative predictive value; FPR: FP rate; FDR: false discovery rate; FNR: FN rate; ACC: accuracy.