Equation 26 shows that the slope re

Equation 26 shows that the slope relating M to Y is (bM20bMZ20Z), which matches the second stage of the indirect effect in Equation 25. Equation 26 also indicates that the intercept of the function relating M to Y, represented by the compound term [b020bZ20Z (bX20bXZ20Z)X], depends on the level of X. For plotting purposes, we suggest the use of the mean of X to compute the intercept. When X is mean-centered, as in the present illustration, the mean of X equals 0, and the intercept simplifies to (b020bZ20Z).Plots for the direct, indirect, and total effects were based on Equation 25, which expresses the direct effect as (bX20bXZ20Z), the indirect effect as (aX5aXZ5Z)(bM20bMZ20Z), and the total effect as [(bX20bXZ20Z) (aX5aXZ5Z)(bM20bMZ20Z)]. These expressions were used as the slopes for each effect. All three effects shared the common intercept of [b020bZ20Z (a05aZ5Z)(bM20bMZ20Z)], which equals the expected value of Y when X equals 0 for each effect. For display purposes, the axes for each figure were converted back to their original (i.e., uncentered) scales, which facilitates interpretation but does not alter the form of the plotted interaction (Aiken & West,1991, p. 15).