In many practical classification problems it is important to distinguish fa
lse positive from false negative results when evaluating the performance of
the classifier. This is of particular importance for medical diagnostic te
sts. In this context, receiver operating characteristic (ROC) curves have b
ecome a standard tool. Here we apply this concept to characterize the perfo
rmance of a simple neural network. Investigating the binary classification
of a perceptron we calculate analytically the shape of the corresponding RO
C curves. The influence of die size of the training set and the prevalence
of the quality considered are studied by means of a statistical-mechanics a
nalysis. [S1063-651X(99)06911-1].