receiver operating characteristic

n. (ROC) In signal detection theory, the relative proportion of correct identifications (hits) and incorrect identifications (false alarms). This is frequently represented as a curve relating the two probabilities as well as chance expectation, from which the signalto-noise ratio is calculated and in which the sensitivity of the system is represented as d′(d prime), which is the area of the curve 
between the curve of performance and the line of chance expectation.