TABLE 4.

Empirical results for estimators of causal effect of each additional unit exposure on outcome for the scenario where $P(X=0)=0.50$

Method	Log-normal				Weibull
	EBIAS	ESE	ASE	ECP	EBIAS	ESE	ASE	ECP
Additive outcome model
Unadjusted	1.18	0.26	0.23	0.01	0.82	0.23	0.16	0.05
Regression adjustment	0.44	0.23	0.18	0.27	0.30	0.17	0.13	0.32
Generalized propensity score	0.44	0.23	0.23	0.48	0.30	0.17	0.16	0.53
Propensity score based on two-part model	0.00	0.22	0.21	0.97	0.00	0.15	0.14	0.96
Multiplicative outcome model
Unadjusted	−1.39	0.23	0.19	0.00	−0.97	0.23	0.17	0.03
Regression adjustment	−0.63	0.24	0.18	0.03	−0.42	0.18	0.14	0.10
Generalized propensity score	−0.63	0.24	0.19	0.04	−0.42	0.18	0.14	0.11
Propensity score based on two-part model	0.00	0.13	0.10	0.95	0.00	0.08	0.07	0.95

^aEBIAS: Empirical bias

^bESE: Empirical standard error

^cASE: Asymptotic standard error

^dECP: Empirical coverage probability