Sensitivity analysis is a simple procedure that is applied after the training phase and analyzes the model responses when the inputs are changed. Originally proposed for NNs, this sensitivity method can also be applied to other algorithms, such as SVM . Let y aj denote the output obtained by holding all input variables at their average values except xa, which varies through its entire range with j ∈ {1,...,L} levels. If a given input variable (xa ∈ {x1,...,xI}) is relevant then it should produce a high variance (Va). Thus, its relative impor- tance (Ra) can be given by