highly significantp < 0.001
Because Levene’s test indicated unequal variances, the association was re-examined using tests that do not assume variance homogeneity or normality; the graded gradient remained highly significant under Welch’s ANOVA ( F = 17.438, df1 = 4, df2 = 76.425, p < 0.001) and the Kruskal–Wallis test ( H = 94.754, df = 4, p < 0.001).