Signal Detectability Theory and the Evaluation of Prediction Tables

The Theory of Signal Detectability (TSD) is a branch of information theory devised to handle problems in the study of communication between information sources and receivers over noisy channels. The user of a criminological prediction device faces a similar problem in having to make decisions, with associated costs and pay-offs, from uncertain evidence.

This application of signal detection theory in the criminological context is discussed with particular reference to (a) the well known base rate problems in prediction studies; (b) the problem of finding indices of predictive power which are independent of the base rate; (c) the various implications and uses of the Receiver Operating Characteristic (ROC) curve in evaluating prediction devices. These properties are illustrated by reference to an example taken from research into the area of juvenile offending.