box plots. In each panel, the median value for each model is depicted by a vertical line inside the box, the grey boxes range from the first quantile (Q1) to the third quantile (Q3), the notch around the median indicates the confidence interval (1.5 × (Q3 − Q1)), the lines extending horizontally from the boxes (whiskers) indicate the minimum and maximum value after removing outliers. Outliers are plotted as stars. Left: six models from top to bottom: log parabola with a combination of N_H, Gal and N_H, z, N_H free and N_H fixed to N_H, Gal, power law with a combination of N_H, Gal and N_H, z, N_H free and N_H fixed to N_H, Gal. Middle: From top to bottom: log parabola and power law models. Right: From top to bottom: models with combination of N_H, Gal and N_H, z, N_H free, and N_H fixed to N_H, Gal.