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Article
February 14, 1977

Decision Analysis

JAMA. 1977;237(7):642-643. doi:10.1001/jama.1977.03270340027008
Abstract

To the Editor.—  The conclusion that decision analysis shows that additional knowledge can be harmful is misleading. Decision analysis in the pancreatic cancer example would show that the attractive-sounding test is useless, not harmful. The test appears harmful in the example because it is misused.The statistics reported for the hypothetical test for pancreatic cancer indicate that 80% of patients who have cancer are detected, while positive results are obtained for only 5% of noncancerous patients. The encouraging impression given by these figures is reversed when Bayes theorem is used to compute the probability that a patient with positive results has cancer:P(C/T) is the probability of cancer if the test result is positive, P(C) is the probability of cancer, P(NC) is the probability of no cancer, P(T/C) is the probability of a positive test if cancer exists, and P(T/NC) is the probability that the test is positive if no

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