The meta-analysis of clinical judgment project:: Fifty-six years of accumulated research on clinical versus statistical prediction

Clinical predictions made by mental health practitioners are compared with those using statistical approaches. Sixty-seven studies were identified from a comprehensive search of 56 years of research; 92 effect sizes were derived front these studies. The overall effect of clinical versus statistical prediction showed a somewhat greater accuracy for statistical methods. The most stringent sample of studies, front which 48 effect sizes were extracted, indicated a 13% increase in accuracy using statistical versus clinical methods. Several variables influenced this overall effect. Clinical and statistical prediction accuracy varied by type of prediction, the setting in which predictor data were gathered, the type of statistical formula used, and the amount of information available to the clinicians and the formulas. Recommedations are provided about when and tinder what conditions counseling psychologists might use statistical formulas to well as when they can rely on clinical methods. Implications for clinical judgement research and training are discussed.