 To estimate the probability that examinees possess specific attributes, given their observed item response pattern, an artificial neural network approach is used.The neural network is a type of parallel-processing architecture that transforms any stimulus received by the input unit (i.e., stimulus units) to a signal for the output unit (i.e., response units) through a series of mid-level hidden units.Each unit in the input layer is connected to each unit in the hidden layer and, in turn, to each unit in the output layer.