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NAEP Technical DocumentationIRT parameters for items in the algebra scale, grade 8 mathematics combined national and state main assessment, by item and block: 2009

Block	Item	NAEP ID	aj	bj	cj	dj1	dj2	dj3	dj4
† Not applicable; c parameters are not estimated for generalized partial credit models, and d parameters are not estimated for two-parameter or three-parameter logistic models. NOTE: For item j, aj represents the discriminatory power of the item, bj represents a location parameter related to item difficulty, cj represents the guessing parameter, and dji represents the category threshold parameter for category i. The c parameter value is exactly zero for items scaled with the two-parameter logistic model. For item j, dji may not sum to zero because of rounding. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2009 Mathematics Assessment.
M3	8	M150501	0.99	0.67	0.22	†	†	†	†
	9	M150601	1.10	1.75	0.09	†	†	†	†
	11	M150801	0.51	1.72	†	-1.77	1.77	†	†
	14	M151101	1.28	0.46	0.04	†	†	†	†
	15	M151201	0.58	1.15	†	†	†	†	†
M4	5	M151701	1.15	0.04	0.20	†	†	†	†
	7	M151901	0.65	0.23	0.04	†	†	†	†
	9	M152101	0.66	0.68	0.17	†	†	†	†
	10	M152201	1.07	0.20	0.20	†	†	†	†
	13	M152501	1.98	1.09	0.13	†	†	†	†
	14	M152602	0.77	0.44	†	1.82	-2.65	0.83	†
M5	6	M019701	0.57	-2.20	†	†	†	†	†
	11	M066501	0.45	-1.19	†	-0.76	0.76	†	†
M6	2	M140501	1.57	-0.21	0.23	†	†	†	†
	6	M140901	0.82	0.08	0.10	†	†	†	†
	12	M141501	1.15	0.10	0.27	†	†	†	†
	16	M141901	0.44	1.68	†	2.28	1.12	-0.83	-2.57
M7	6	M169401	0.94	0.66	0.18	†	†	†	†
	10	M164201	1.00	1.32	0.15	†	†	†	†
	11	M170201	1.20	0.71	0.29	†	†	†	†
	12	M165301	0.94	0.74	†	0.12	-0.12	†	†
M8	3	M163301	0.99	-0.32	0.25	†	†	†	†
	5	M164501	0.92	-0.07	0.13	†	†	†	†
	12	M166601	0.81	0.25	0.13	†	†	†	†
	15	M1699CL	0.52	-0.38	†	0.80	1.96	-0.21	-2.55
M9	3	M170601	0.53	-0.78	0.10	†	†	†	†
	10	M170701	1.56	0.63	0.24	†	†	†	†
	11	M165001	0.81	1.30	†	†	†	†	†
	13	M170801	0.85	2.22	†	-1.73	1.73	†	†
M10	1	M142001	0.78	0.53	0.50	†	†	†	†
	7	M142601	1.15	-0.32	0.26	†	†	†	†
	8	M142701	1.10	0.15	0.08	†	†	†	†
	9	M142801	0.75	0.93	†	†	†	†	†
	14	M143301	1.24	0.41	0.24	†	†	†	†
M11	6	M171001	1.03	1.57	0.48	†	†	†	†
	9	M168301	0.73	0.75	†	-0.52	0.52	†	†
	12	M164701	0.99	1.65	0.28	†	†	†	†
	14	M165201	1.65	1.24	0.18	†	†	†	†
	17	M104901	0.71	1.57	†	0.73	-0.73	†	†
M12	5	M153101	0.96	0.40	0.20	†	†	†	†
	7	M153301	1.64	1.14	0.13	†	†	†	†
	9	M153501	0.57	-0.83	0.12	†	†	†	†
	10	M153601	0.78	-0.96	†	†	†	†	†
	12	M153801	1.84	0.94	0.13	†	†	†	†
	15	M154101	0.79	0.70	0.20	†	†	†	†
	17	M154301	1.89	1.25	0.17	†	†	†	†

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