Fig. 1From: Required sample size to detect mediation in 3-level implementation studiesSingle-level mediation model. Note: X = independent variable; M = mediator, Y = outcome. The indirect effect is estimated as the product of the a and b paths (i.e., a*b). The c’ path represents the direct effect of X on Y (i.e., the effect of X on Y that is not transmitted through the mediator, M)Back to article page