The structure of diagnostic information

Diagnosis is characterized as an exercise in classification, where the task is to assign a crop to a risk group as a basis for evidence-based crop protection decision making. Underlying the process of diagnostic decision making is Bayesian updating of probabilities. Alongside updating of probabilities, assessments of diagnostic information allow further description of the characteristics of diagnostic tests, and of the predictions made on the basis of test outcomes. This is illustrated analytically, graphically (by means of isoinformation contour plots and information graphs) and by discussion of example epidemiological scenarios.