AN EXTENSION OF THE SIGNAL DETECTION MODEL OF INFORMATION RETRIEVAL

Abstract

It is suggested that a possible reason for receiver‐operating characteristics (ROC) curves having a slope other than unity when plotted on Normal‐deviate axes is that the dichotomy into relevant and non‐relevant items is artificial, and that there is really a bivariate distribution of objective relevance and relevance as assessed by the IR system, with positive correlation. This correlation is the appropriate measure of the effectiveness of the IR system, and can be calculated from the shape of the ROC curve.