Table 5.

Performance measures.

Performance measures	Definition of the measure	Description
Sensitivity (or) Recall (or) True positive rate (or) Probability of detection (pd)	$\frac{\mathrm{T}\mathrm{P}}{\mathrm{T}\mathrm{P}+\mathrm{F}\mathrm{N}}$	Proportion of defective modules correctly predicted
Precision	$\frac{\mathrm{T}\mathrm{P}}{\mathrm{T}\mathrm{P}+\mathrm{F}\mathrm{P}}$	Proportion of modules predicted as defective
False positive rate (or) Probability of false alarm (pf)	$\frac{\mathrm{F}\mathrm{P}}{\mathrm{F}\mathrm{P}+\mathrm{T}\mathrm{N}}$	Proportion of nondefective modules predicted as defective
Specificity	$\frac{\mathrm{T}\mathrm{N}}{\mathrm{T}\mathrm{N}+\mathrm{F}\mathrm{P}}$	Proportion of correctly predicted nondefective modules
Classification accuracy	$\frac{\mathrm{T}\mathrm{N}+\mathrm{T}\mathrm{P}}{\mathrm{T}\mathrm{N}+\mathrm{F}\mathrm{N}+\mathrm{F}\mathrm{P}+\mathrm{T}\mathrm{P}}\phantom{\frac{{\mathrm{T}\mathrm{N}+\mathrm{T}\mathrm{P}}^{XX}}{\mathrm{T}\mathrm{N}+\mathrm{F}\mathrm{N}+\mathrm{F}\mathrm{P}+{\mathrm{T}\mathrm{P}}_{XX}}}$	Proportion of correctly predicted modules
Balance	$\mathrm{1}-\frac{\sqrt{(\mathrm{0}-\mathrm{p}\mathrm{f}{)}^{\mathrm{2}}+(\mathrm{1}-\mathrm{p}\mathrm{d}{)}^{\mathrm{2}}}}{\sqrt{\mathrm{2}}}$	Balance combines pf and pd into one measure and is defined as the distance from the ROC “sweet spot” (where pd = 1 and pf = 0)
Receiver Operating Characteristics (ROC) curve	A graphical plot of “pd” versus “pf” where the discrimination threshold is varied