1. A method for generating a prediction result for use on a specific subject to predict a biological attribute of that subject using spectroscopy as a surrogate indirect measurement for a direct measurement of said biological attribute, said method comprising the steps of: (a) acquiring a calibration data set and modifying said calibration data set in a manner that reduces the spectral variation due to subject specific attributes; (b) generating a model by applying multivariate analysis to said. modified calibration data set; and (c) using a prediction process to predict an unknown amount of said biological attribute in a target spectroscopic measurement from said specific subject, said prediction process utilizing said model in conjunction with one or more reference measurements.