Statistical Risk Assessment: Old Problems and New Applications

Abstract

Statistically based risk assessment devices are widely used in criminal justice settings. Their promise remains largely unfulfilled, however, because assumptions and premises requisite to their development and application are routinely ignored and/or violated. This article provides a brief review of the most salient of these assumptions and premises, addressing the base rate and selection ratios, methods of combining predictor variables and the nature of criterion variables chosen, cross-validation, replicability, and generalizability. The article also discusses decision makers’ choices to add or delete items from the instruments and suggests recommendations for policy makers to consider when adopting risk assessments. Suggestions for improved practice, practical and methodological, are made.