Table 6.

Measures of diagnostic accuracy, sensitivity, and bias based on the frequencies of hits (H), misses (M), correct rejections (CR), and false alarms (FA), obtained from the discriminant function analyses. Note: z(HR), z(FR) = inverse normal transformation of the hit and false alarm rates.

Measure	Form
Diagnostic sensitivity (hit rate, HR)	$\frac{H}{H+M}$
Diagnostic specificity	$\frac{\mathit{CR}}{\mathit{FA}+\mathit{CR}}=1-\mathit{FR}$
Positive predictive value	$\frac{H}{H+\mathit{FA}}$
Negative predictive value	$\frac{\mathit{CR}}{\mathit{CR}+M}$
2AFC d′ (sensitivity)	$\frac{1}{\sqrt{2}}[z\left(\mathit{HR}\right)-z\left(\mathit{FR}\right)]$
2AFC c (bias)	$\frac{1}{2\sqrt{2}}[z\left(\mathit{HR}\right)+z\left(\mathit{FR}\right)]$