Table 1.

Simulation results for 500 Monte Carlo datasets

Estimator	DIF	CM		GPS
	abs bias	abs bias	Coverage	abs bias	Coverage
$\widehat{\tau }(1,2)$	0.6790	0.0264	$92\%$	0.0597	$100\%$
$\widehat{\tau }(1,3)$	0.4668	0.1662	$92\%$	0.3742	$99\%$
$\widehat{\tau }(1,4)$	0.8172	0.2398	$96\%$	0.4811	$100\%$
$\widehat{\tau }(2,3)$	0.2122	0.1398	$95\%$	0.3145	$99\%$
$\widehat{\tau }(2,4)$	0.1382	0.2134	$97\%$	0.4214	$100\%$
$\widehat{\tau }(3,4)$	0.3504	0.0736	$98\%$	0.1069	$100\%$

DIF is the sample difference. CM is the covariates matching estimator. GPS is the generalized propensity score matching estimator. “abs bias” is $\mid E(\widehat{\tau })-\tau \mid$