Table 1.

Simulation results for path a, the effect of treatment on the mediator (population value = 1.0).

	All confounders	Half of confounders	No confounders
N = 100
Mean	1.068	0.997	0.709
Bias	0.068	−0.003	−0.291
Rel. Bias	0.068	−0.003	−0.291
SD	0.560	0.537	0.423
MSE	0.318	0.289	0.264
N = 250
Mean	1.035	0.976	0.689
Bias	0.035	−0.024	−0.311
Rel. Bias	0.035	−0.024	−0.311
SD	0.329	0.321	0.255
MSE	0.110	0.104	0.162
N = 500
Mean	0.998	0.939	0.664
Bias	−0.002	−0.061	−0.336
Rel. Bias	−0.002	−0.061	−0.336
SD	0.228	0.217	0.178
MSE	0.052	0.051	0.144
N = 1000
Mean	1.002	0.942	0.666
Bias	0.002	−0.058	−0.334
Rel. Bias	0.002	−0.058	−0.334
SD	0.172	0.166	0.137
MSE	0.029	0.031	0.130