Table 1.

Estimates of Bias for the Component r² Measures for Mediation

Parameter	True Value	Sample Size
		50	100	200	300	500	1,000
$r_{XM}^2$	α = 0	.020	.010	.005	.003	.002	.001
	α = .14	.019	.009	.005	.003	.002	.001
	α = .39	.013	.007	.003	.002	.001	.000
	α = .59	.008	.004	.001	.002	.001	.001
$r_{YM.X}^2$	β = 0	.021	.010	.005	.003	.002	.001
	β = .14	.020	.001	.005	.003	.002	.001
	β = .39	.015	.001	.003	.002	.002	.001
	β = .59	.008	.004	.002	.001	.000	.000
$r_{YX.M}^2$	τ′ = 0	.020	.010	.005	.003	.002	.001
	τ′ = .14	.020	.010	.005	.003	.002	.001
	τ′ = .39	.014	.007	.004	.002	.001	.001
	τ′ = .59	.009	.005	.002	.001	.001	.000

Note—Estimates of bias for each component r² measure for mediation are collapsed across simulation parameters by which bias was not affected.