1. A method for multivariate analysis using a mathematical model for generating model data and actual data for more than one variable, wherein the model data is substantially representative of more than one variable, said method comprising: for each variable, determining a difference between the model data and the actual data; for each variable, determining a fractional impact on performance; for each variable, determining a weighted deviation based on the determined difference and the determined fractional impact; and transmitting the weighted deviation to an output device.