Sensitivity index
= Sensitivity index
{title2=$d'=(\mu_s-\mu_n)/\sigma$}
Under an equal-variance Gaussian evidence model, $d'$ is separation of signal and noise means in units of their common <standard deviation>. A yes/no task gives $d'=\Phi^{-1}(H)-\Phi^{-1}(F)$, where $H$ and $F$ are hit and false-alarm <probabilities>. This formula assumes the model; it does not define every possible sensory-discrimination measure.