d′ (Sensitivity)

SDT discriminability of a binary appraiser — how well they distinguish OK from NOK, independent of their decision threshold.

Also known as: d-prime, sensitivity index

$d^{'}$ ("d-prime") measures the pure discriminability of a binary appraiser. From hit rate $h$ and false-alarm rate $f$ :

d^{'} = z (h) - z (f)

$z (\cdot)$ is the standard-normal quantile function. $d^{'} = 0$ : no discriminability (guessing). $d^{'} = 1$ : modest. $d^{'} ≳ 3$ : very good. Crucially, $d^{'}$ is independent of the decision threshold c — an appraiser can be very discriminating yet pick an unfavourable threshold.

Used in

MSA Type 5 (attribute)

In the Algorithm Lab

msa/signal-detection

Sources

Green, D.M. & Swets, J.A. (1966). Signal Detection Theory and Psychophysics. Wiley.

d′ (Sensitivity)

See also

Used in

In the Algorithm Lab

Sources