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NAEP Analysis and Scaling → Estimation of NAEP Score Scales → NAEP Assessment IRT Parameters → Science Assessment IRT Parameters → IRT Parameters for Items in the Life Science Subscale, Grade 8 Science Combined National and State Assessment, by Item and Block: 2015

NAEP Technical DocumentationIRT Parameters for Items in the Life Science Subscale, Grade 8 Science Combined National and State Assessment, by Item and Block: 2015

IRT parameters for items in the life science subscale, grade 8 science combined national and state assessment, by item and block: 2015
Block	Item	NAEP ID	a_j	b_j	c_j	d_j₁	d_j₂	d_j₃	d_j₄
S3	6	K113401	0.35	0.69	†	-0.08	-0.28	2.36	-2.00
	12	K113001	1.24	-0.13	0.40	†	†	†	†
	13	K113801	0.87	0.30	0.38	†	†	†	†
	17	K113501	0.70	0.45	0.32	†	†	†	†
S4	1	K117801	1.35	-0.67	0.41	†	†	†	†
	4	K122301	0.90	0.56	0.24	†	†	†	†
	5	K122302	1.23	0.35	0.42	†	†	†	†
	6	K122303	0.92	1.59	0.28	†	†	†	†
	7	K122304	1.91	0.78	0.25	†	†	†	†
	13	K122801	0.73	1.11	†	0.41	-0.41	†	†
	16	K125201	0.35	0.27	†	0.06	0.73	-1.65	0.86
S5	3	K154501	1.03	0.07	0.25	†	†	†	†
	9	K118501	0.55	0.99	†	1.18	-0.09	-1.09	†
	10	K154601	0.52	0.21	†	0.71	-0.71	†	†
	15	K154701	0.60	1.15	†	3.06	-0.48	-0.54	-2.04
	16	K154801	0.95	-0.75	0.26	†	†	†	†
	18	K120501	1.51	-0.18	0.32	†	†	†	†
S6	2	K124501	1.50	0.61	0.26	†	†	†	†
	4	K123801	0.73	0.43	†	0.59	-0.18	-0.41	†
	5	K123802	0.46	0.35	†	0.75	-0.75	†	†
	11	K155001	1.60	-0.29	0.36	†	†	†	†
	16	K155301	1.62	0.56	0.39	†	†	†	†
S7	2	K117401	1.39	0.69	0.14	†	†	†	†
	6	K110601	1.24	-0.60	0.38	†	†	†	†
	12	K110501	0.74	1.17	†	0.86	-0.86	†	†
	13	K121001	0.89	1.40	†	0.30	-0.30	†	†
	14	K1210CL	0.43	0.53	†	-1.03	1.98	-0.94	†
S8	1	K112801	1.20	-0.35	0.39	†	†	†	†
	8	K119701	1.61	0.55	0.28	†	†	†	†
	14	K111601	0.71	0.22	0.19	†	†	†	†
	16	K155801	1.64	-0.11	0.38	†	†	†	†
	18	K155901	0.73	0.22	0.36	†	†	†	†
S9	2	K114401	1.35	0.42	0.20	†	†	†	†
	8	K114802	0.61	0.27	†	-0.36	0.36	†	†
	9	K114801	0.37	1.75	†	-1.25	2.45	-1.21	†
	12	K124102	0.42	0.49	†	-1.06	1.67	-0.61	†
S10	2	K170501	0.90	-0.95	0.26	†	†	†	†
	6	K168801	0.74	0.29	0.39	†	†	†	†
	8	K169301	1.26	-0.03	0.40	†	†	†	†
	10	K172101	0.48	-0.53	†	0.16	-0.16	†	†
	17	K170801	1.22	-0.02	0.34	†	†	†	†
S11	1	K165701	0.74	-1.16	0.40	†	†	†	†
	6	K169001	1.00	-0.23	0.30	†	†	†	†
	11	K167401	1.32	-0.17	0.41	†	†	†	†
S12	7	K123301	0.81	0.24	0.00	†	†	†	†
S12	12	K112601	0.71	1.92	†	0.68	-0.68	†	†
† Not applicable; c parameters are not estimated for the two-parameter logistic model or generalized partial credit models, and d parameters are not estimated for two-parameter or three-parameter logistic models. NOTE: For item j, a_j represents the discriminatory power of the item, b_j represents a location parameter related to item difficulty, c_j represents the guessing parameter, and d_j_i represents the category threshold parameter for category i. The c parameter is assumed to be exactly zero and is not estimated for items scaled with the two-parameter logistic model. For item j, d_ji 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), 2015 Science Assessment.

Last updated 17 November 2021 (ML)

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