χ² values of the fit when varying in the model. The horizontal dashed line separates the statistically worse models (over the line) from the best models (below the dashed lines). The models below the dashed lines are statistically equivalent within 1σ (68% confidence level for the red line) and 2σ (95% confidence level for the green line). Note: the significantly larger χ² at . The high amount of local minima is an indication of the complexity of the problem.