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the accuracy of predictions made by professionals, by machines, and by simple rules. You will not be surprised by our conclusion that the professionals come third in this competition.
noise is a major factor in the inferiority of human judgment.
percent concordant (PC), which answers a more specific question: Suppose you take a pair of employees at random. What is the probability that the one who scored higher on an evaluation of potential also performs better on the job?
most judgments are made in a state of what we call objective ignorance, because many things on which the future depends can simply not be known.
clinical judgment. You consider the information, perhaps engage in a quick computation, consult your intuition, and come up with a judgment.
Meehl’s results strongly suggest that any satisfaction you felt with the quality of your judgment was an illusion: the illusion of validity.
If you find yourself confused by the distinction between cases and predictions, you are in excellent company: Everybody finds that distinction confusing.
If you are as confident in your predictions as you are in your evaluation of cases, however, you are a victim of the illusion of validity.
The findings support a blunt conclusion: simple models beat humans.
people are inferior to statistical models in many ways. One of their critical weaknesses is that they are noisy.
