If the coefficients c3, c4, and c6 shall be included in the collector model, can be determined by the T-ratio
(parameter value / standard deviation of parameter value) of the parameter identification. The T-ratio
should be greater than 3 for those parameters presented in the test results. If the T-ratio is less than 3,
(enough variability in the input data are assumed), the coefficient shall be set to zero and the parameter
identification should be repeated with the adjusted collector model.