Relationship between (v²), an estimate of MoE, and DEN for 635 logs. Part A shows the relationship between the variables when age is ignored (R² = 0.68). Part B separates the observations in three age classes: under 15 years (o), greater than 15 and lower than 25 years (+), and over 25 years of age (▽). The explained proportion of variation is much lower for young trees (R² = 0.08).