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NAEP Technical DocumentationIRT parameters for items in the geometry 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	3	M150001	1.03	0.98	0.47	†	†	†	†
	6	M150301	1.34	0.39	0.11	†	†	†	†
M4	1	M151301	0.87	-0.59	0.10	†	†	†	†
	3	M151501	0.74	-0.33	†	0.30	-0.30	†	†
M5	1	M085701	0.42	-0.68	†	†	†	†	†
	2	M085901	0.52	-0.26	†	1.22	-1.22	†	†
	5	M085801	0.75	-0.18	0.23	†	†	†	†
	15	M019601	0.86	0.89	0.16	†	†	†	†
M6	3	M140601	0.73	-1.21	0.25	†	†	†	†
	9	M141201	0.70	0.77	0.17	†	†	†	†
	11	M141401	0.60	0.80	0.16	†	†	†	†
	14	M141701	0.86	1.11	0.11	†	†	†	†
M7	4	M170101	0.17	-0.58	†	-5.75	5.75	†	†
	7	M168201	0.89	0.42	0.18	†	†	†	†
	15	M168401	1.18	1.85	0.12	†	†	†	†
M8	2	M167801	0.85	0.15	0.15	†	†	†	†
	11	M170501	0.48	-0.37	†	-1.10	1.10	†	†
	13	M164901	0.92	0.94	0.08	†	†	†	†
	14	M166901	1.28	1.37	0.36	†	†	†	†
M9	2	M166401	1.43	0.22	0.29	†	†	†	†
	7	M166701	0.62	0.07	0.18	†	†	†	†
	12	M124901	0.76	0.33	0.29	†	†	†	†
	14	M124001	1.21	1.25	0.11	†	†	†	†
M10	3	M142201	0.81	-0.54	0.14	†	†	†	†
	15	M143401	0.99	0.70	0.23	†	†	†	†
	16	M143501	0.46	0.94	†	2.07	-0.91	-1.98	0.82
M11	2	M170901	0.96	-0.23	0.20	†	†	†	†
	10	M169101	0.91	2.28	0.34	†	†	†	†
	16	M171201	0.89	1.17	0.15	†	†	†	†
M12	1	M152701	1.25	-0.32	0.22	†	†	†	†
	4	M153001	0.96	-0.46	0.27	†	†	†	†
	8	M153401	0.90	1.20	0.20	†	†	†	†
	14	M154001	0.74	0.43	0.09	†	†	†	†

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