Experimental values ( y ) as a function of predicted responses ( ŷ ) for the 2nd-round of modeling. The diagonal full straight line and the curved dotted lines indicate a perfect match of the model (y = ŷ) and the 95%-confidence intervals of the whole-model ANOVA test, respectively. The horizontal dotted straight line represents the mean of the response as experimentally observed. The value indicated in parentheses is the RMSEF standardized in terms of percentage of the average scale of the response (i.e. the difference between the mean and the minimal experimental values). R2 adj., R2 adjusted.