Based on the equivalence test, the statistical parameters of the intra-class correlation coefficient (r) and the inter-rater coefficient of determination (R2) were significantly enhanced when raters used the SADs to estimate powdery mildew severity on leaflets. With aid of the diagrams, r2advanced from r 1⁄4 0.689 to r 1⁄4 0.868 (Table 3). Similarly, the R mean of the pairwise comparisons increased from 0.83 to 0.89 (Table 3), indicating that use of the diagrams improved inter-rater reliability.