Figure 9: Six images were found, which were clearly outliers (A–F). An outlier analysis was performed, paying attention to: (G) the influence of each particular image on the final model according to Cook’s distance measure, (H) the studentized residuals (residuals divided by their estimated standard deviation), (I) the p-values of the outlier test (Bonferroni correction) and (J) the hat-values in order to identify influential observations.