Assignment of data into a defined mathematical description invariably associated with a priori assumptions
Formal process of defining data within a mathematical definition enabling significant insight and possibly predictive power into the data set. However, the model comprises a priori assumptions which the data must not violate. For example in phylogenetics the model depends on each mutation being independent of the occurance of any other mutation. Parametric statistics are a model assuming a normal distribution of the data. If the assumption is strongly violated the model is invalidated regardless of result.
