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Given a data set about an individual or group (e.g., interviewer ratings, life history or demographic facts, test results, self-descriptions), there are two modes of data combination for a predictive or diagnostic purpose. The clinical method relies on human judgment that is based on informal contemplation and, sometimes, discussion with others (e.g., case conferences). The mechanical method involves a formal, algorithmic, objective procedure (e.g., equation) to reach the decision. Empirical comparisons of the accuracy of the two methods (136 studies over a wide range of predictands) show that the mechanical method is almost invariably equal to or superior to the clinical method: Common antiactuarial arguments are rebutted, possible causes of widespread resistance to the comparative research are offered, and policy implications of the statistical method’s superiority are discussed. In 1928, the Illinois State Board of Parole published a study by sociologist Burgess of the parole outcome for 3,000 criminal offenders, an exhaustive sample of parolees in a period of years preceding. (In Meehl 1954/1996, this number is erroneously reported as 1,000, a slip probably arising from the fact that 1,000 cases came from each of three Illinois prisons.) Burgess combined 21 objective factors (e.g., nature of crime,
Grove et al. (Sat,) studied this question.