Table 1. Average statistical bias as defined by (5), correlation between average figure of merit (FOM) of a data set and mean cosine of the phase error (CPEM) of a data set, r.m.s. error of direct estimation of CPEM by FOM and r.m.s. error of a cross-correlated kernel regression estimation of CPEM by FOM.

FOM and CPEM are calculated after 20 cycles of density modification by Parrot with MULTICOMB MLHL phase combination, by SOLOMON with MULTICOMB SAD–DM phase combination and by Pirate for all 102 data sets.

	Parrot + MLHL		SOLOMON + SAD–DM
	Original	With β correction	Original	With β correction	Pirate
Average bias	0.280	0.143	0.250	0.099	0.181
Correlation of FOM and CPEM	0.650	0.901	0.618	0.904	0.621
R.m.s. estimation error	0.316	0.166	0.305	0.137	0.219
R.m.s. regression estimation error	0.145	0.079	0.173	0.083	0.126