Boxplots representing the models’ error distributions in respect to the prediction step. The box has lines at the lower quartile, median (red line) and upper quartile values. Whiskers extend from each end of the box to the adjacent values in the data; in our case to the most extreme values within 1.5 times the interquartile range from the ends of the box. Outliers (e.g. data with values beyond the ends of the whiskers) are not displayed for visualization purposes, but they are distributed symmetrically in respect to the median in each case and may reach ±6 MHz for both models.