Analyzing Use of Diagnostic Signs

This paper presents a technique–diagnostic strategy analysis–for describing a physician's reliance on signs when making a diagnostic judgment. Use of the technique is demonstrated by a study in which nine radiologists judged the malignancy of gastric ulcers on the basis of seven roentgenologic signs. The technique proved capable of describing each radiologist's use of signs in a precise quantitative way. These descriptions enabled disagreements among radiologists to be traced to individual differences in the use of signs. In addition, each radiologist's use of signs was compared with statistical evidence pertaining to the validity of these signs. The present technique seems to have promise as a teaching device that would enable students to see precisely why their judgments differ from those of their expert instructor. It even may provide the expert with new insight into his own inferential processes.