TABLE 1.

RMSE for EB ComBat, Non‐EB ComBat, and PEACE as a function of sample size is shown for the simulation experiment with $Z=1$ (left) and $Z=2$ (right). PEACE achieves the lowest RMSE.

	$Z=1$				$Z=2$
	$I=75$	$I=150$	$I=300$	$I=600$	$I=75$	$I=150$	$I=300$	$I=600$
Unharmonized	15.07	16.69	17.37	19.35	33.58	28.6	29.88	32.92
EB ComBat	1.51	1.69	1.62	1.40	2.88	6.30	3.14	3.05
Non‐EB ComBat	0.76	1.32	1.00	0.61	2.57	6.22	3.06	2.99
PEACE	0.48	0.63	0.39	0.18	1.83	1.17	0.25	1.25

Abbreviations: EB ComBat, ComBat with empirical Bayes; Non‐EB ComBat, ComBat without empirical Bayes; PEACE, Probabilistic Estimation for Across‐batch Compatibility Enhancement; RMSE, root mean square error.