In Figure 2.8, the direct effect is represented by the path coefficient p, corresponding to the path P → X. The bias due to litter size corresponds to the path P ← L → Q → X. And now the algebraic magic: the amount of bias is equal to the product of the path coefficients along that path (in other words, l times lʹ times q). The total correlation, then, is just the sum of the path coefficients along the two paths: algebraically, p + (l × lʹ × q) = 5.66 grams per day.
