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NAEP Technical DocumentationIRT parameters for items in the life science scale, grade 4 science 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 Science Assessment.
S3	3	K077602	0.53	0.31	†	0.84	-0.41	-0.43	†
	4	K077603	0.90	1.66	0.32	†	†	†	†
	8	K080501	0.88	-0.21	0.22	†	†	†	†
	9	K080502	0.43	0.87	0.20	†	†	†	†
	12	K153101	0.70	1.03	0.17	†	†	†	†
	13	K153102	0.30	4.33	†	†	†	†	†
S4	3	K078701	0.95	0.98	0.07	†	†	†	†
	5	K084301	0.59	0.44	†	†	†	†	†
	6	K084302	0.75	0.14	†	†	†	†	†
	7	K153201	0.60	-2.09	0.23	†	†	†	†
	8	K153301	0.74	-0.05	†	0.93	-0.93	†	†
	14	K084401	0.79	-0.33	0.15	†	†	†	†
	15	K153401	0.65	-1.38	0.30	†	†	†	†
S5	3	K081601	0.54	2.26	†	-0.37	0.37	†	†
	4	K087301	0.49	-0.38	†	1.22	-1.22	†	†
	6	K081901	0.87	2.76	0.17	†	†	†	†
	12	K153501	0.69	1.24	0.20	†	†	†	†
	13	K153502	0.76	1.02	0.26	†	†	†	†
	14	K082501	0.39	-0.08	†	1.27	-1.27	†	†
S6	4	K086601	0.37	1.29	0.25	†	†	†	†
	5	K086602	0.66	1.04	0.25	†	†	†	†
	11	K087402	0.26	1.54	†	3.64	-0.13	-3.51	†
	14	K108701	0.59	-1.70	0.18	†	†	†	†
S7	1	K076001	0.95	-1.02	0.19	†	†	†	†
	3	K076801	0.56	-0.48	0.17	†	†	†	†
	4	K076802	0.71	-0.68	0.22	†	†	†	†
	7	K080703	0.55	2.51	†	0.53	1.16	-1.69	†
	14	K077301	0.76	-0.26	0.35	†	†	†	†
S8	1	K078601	0.86	-1.83	0.15	†	†	†	†
	8	K109301	1.12	1.37	0.24	†	†	†	†
	11	K082401	1.08	1.40	0.41	†	†	†	†
	12	K082402	1.38	1.64	0.28	†	†	†	†
	14	K078201	1.00	0.32	0.17	†	†	†	†
	16	K085801	1.24	-0.33	0.17	†	†	†	†
S9	1	K088701	0.15	-6.41	0.25	†	†	†	†
	2	K088001	0.76	-0.28	0.25	†	†	†	†
	5	K088301	0.30	-4.13	0.21	†	†	†	†
	6	K088302	0.33	-0.55	†	2.00	-2.00	†	†
	9	K109501	1.07	0.69	0.24	†	†	†	†
	14	K1537CL	0.46	-0.78	†	0.16	1.95	-2.11	†
S10	1	K153801	0.39	-3.35	0.22	†	†	†	†
	3	K0829CL	0.59	-0.43	†	2.34	1.46	-1.73	-2.07
	9	K083501	0.68	-1.19	0.18	†	†	†	†
	10	K083502	0.45	0.65	†	1.61	-1.61	†	†
	15	K083402	0.49	1.33	†	0.87	1.00	-1.87	†
S11	3	K085201	0.53	-0.70	0.16	†	†	†	†
	8	K106301	0.58	2.30	†	1.42	2.36	-1.07	-2.70
	9	K076201	0.43	2.03	†	-0.38	0.38	†	†

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