indirect effects. In the simple case, partial mediation by a single variable (i.e., a partial indirect effect) is evaluated in relation to the Z-distribution, with the ratio of the product of the component path coefficients (i.e., the a and b paths in the traditional causal steps approach; Baron and Kenny, 1986; Judd and Kenny, 1981) over the normal-theory standard error for that product. When assessing the total indirect effect operating through multiple mediators, the sum of the products of those coefficients taken over the square root of the asymptotic variance of the sum of those products provides a ratio to be evaluated in relation to the Z-distribution.
