Table 2.

Parameter Recovery of Subpopulation Ms and SDs for Groups 2 and 3.

			Dichotomous								Polytomous
			Subpopulation M				Subpopulation SD				Subpopulation M				Subpopulation SD
			Group2		Group3		Group2		Group3		Group2		Group3		Group2		Group3
Dist.	Design	N	RMSE	Est.	RMSE	Est.	RMSE	Est.	RMSE	Est.	RMSE	Est.	RMSE	Est.	RMSE	Est.	RMSE	Est.
Equivalent	Common-item	100	.28	.19	.18	.09	.19	.83	.13	.90	.20	.20	.09	−.07	.36	1.35	.39	1.38
		200	.27	.10	.27	.07	.14	.87	.12	.90	.10	−.09	.17	−.17	.31	1.31	.38	1.37
		400	.27	.17	.23	.18	.15	.85	.14	.87	.04	.03	.07	.07	.22	.83	.20	.87
		800	.20	.08	.20	.09	.14	.90	.13	.95	.03	.01	.05	.02	.11	.94	.18	.88
	Standard	100	.21	.18	.13	−.04	.20	.81	.19	.87	.23	.19	.17	−.09	.35	1.32	.52	1.38
		200	.11	−.08	.15	−.14	.12	.92	.14	.96	.10	−.08	.20	−.13	.31	1.28	.42	1.32
		400	.06	.04	.11	.10	.14	.88	.14	.89	.02	.02	.06	.12	.13	1.09	.26	1.12
		800	.02	.01	.04	.04	.13	.92	.12	.92	.01	.01	.03	.03	.19	.90	.18	.92
	Block-interlaced	100	.19	.19	.10	−.03	.20	.81	.15	.84	.20	.22	.11	−.13	.32	1.35	.39	1.51
		200	.10	−.07	.16	−.07	.11	.89	.08	.90	.08	−.09	.14	−.18	.28	1.31	.33	1.42
		400	.05	.03	.11	.09	.13	.87	.12	.87	.04	.01	.12	.05	.10	.60	.12	.64
		800	.02	.01	.05	.05	.09	.95	.07	.96	.03	.02	.08	.01	.06	.95	.05	.97
Non-equivalent	Common-item	100	.54	−.25	.42	−.39	.33	.69	.15	.87	.11	−.59	.31	−.80	.26	1.26	.45	1.45
		200	.61	−.15	.38	−.28	.13	.89	.15	.87	.13	−.62	.31	−.80	.36	1.36	.33	1.32
		400	.33	−.35	.35	−.32	.09	.92	.10	.93	.13	−.41	.15	−.38	.20	.81	.20	.82
		800	.26	−.45	.27	−.54	.10	.95	.10	.95	.12	−.48	.13	−.46	.16	.94	.16	.94
	Standard	100	.19	−.36	.16	−.45	.29	.75	.21	.85	.12	−.59	.33	−.79	.26	1.26	.46	1.46
		200	.11	−.47	.13	−.58	.08	.95	.15	.94	.13	−.61	.29	−.78	.39	1.34	.40	1.31
		400	.08	−.53	.09	−.49	.07	.97	.13	.97	.06	−.64	.09	−.60	.16	1.21	.13	1.21
		800	.05	−.50	.06	−.49	.06	.96	.09	.96	.06	−.48	.05	−.47	.08	.94	.10	.96
	Block-interlaced	100	.18	−.37	.48	−.50	.27	.72	.21	.81	.11	−.60	.30	−.81	.26	1.25	.47	1.45
		200	.06	−.45	.11	−.56	.07	.94	.09	.87	.12	−.62	.28	−.78	.34	1.39	.31	1.40
		400	.06	−.54	.05	−.50	.05	.95	.06	.90	.14	−.45	.10	−.42	.21	.87	.22	.90
		800	.07	−.54	.05	−.50	.07	.98	.07	.98	.05	−.50	.03	−.47	.10	.95	.11	.95

Note. Dist. = subpopulation trait distribution conditions; Design = anchor-item design; N = sample size per group; RMSE = root mean square error; Est. = parameter estimates; Equivalent = trait distribution for all groups is N(0, 1); non-equivalent = trait distribution for Group 1 is N(0, 1) and trait distribution for Groups 2 and 3 is N(−0.5, 1).