Fig. 3

Relative bias (upper plots) and empirical standard error (lower plots) for model fits. The graphs on the left illustrate the errors for the parameter estimation \(\hat {E}_{s}\) for each of the three models and the graphs on the right for the contamination range \(\hat {\theta }\) that only exists for the sigmoid models \(\mathcal {S}\) and \(\mathcal {S}_{RE}\). Depicted on the x-axis are 10 different levels of parameter variation for E_s and θ