In this way, the number of variables was reduced from 1326 to 56. A new model generated with these variables, PLS-2, had three principal components, with an R 2 of 0.84 and a Q 2 of 0.84. Validation by permutation testing -scrambling the Y variables while keeping the X-matrix unchanged -indicated that this correlation would be very unlikely to be observed by chance, as expected given the large number of observations on which the model is based.