A system and method for modeling bio-signals in the form of non-linear stochastic oscillators by extracting time series data from a subject into a series of summary fit parameters and comparing the unknown fit parameters to a set of normative fit parameters to determine whether the subject should be included in a group or not. The method includes data collection, feature extraction and then comparison of fit parameters from a non-linear stochastic oscillator model to a normative standard to make the in or out determination for a particular group. The system includes a processor programmed to perform the steps of the method.