d-prime

D-prime (d') is a statistical measure used in signal detection theory to quantify how well someone can distinguish between two different types of signals or stimuli—like detecting a faint sound or identifying a specific image. It represents the difference in sensitivity between signal and noise, with higher values indicating better discrimination. Essentially, d' accounts for both how often a person correctly detects the signal and how often they mistakenly think they see it when it’s not there. It helps researchers understand true perceptual ability, independent of guessing or response biases.