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 Scale, Grade 8 Science Combined National and State Assessments, by Item and Block: 2011

NAEP Technical DocumentationIRT parameters for items in the life science scale, grade 8 science combined national and state assessments, by item and block: 2011

Block	Item	NAEP ID	aj	bj	cj	dj1	dj2	dj3	dj4	dj5
† 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), 2011 Science Assessment.
SC	6	K113401	0.32	0.76	†	-0.12	-0.19	2.53	-2.23	†
	12	K113001	1.14	-0.15	0.35	†	†	†	†	†
	13	K113801	0.73	0.25	0.35	†	†	†	†	†
	17	K113501	0.58	0.43	0.27	†	†	†	†	†
SD	1	K117801	1.24	-0.70	0.36	†	†	†	†	†
	4	K122301	0.78	0.72	0.24	†	†	†	†	†
	5	K122302	1.25	0.51	0.43	†	†	†	†	†
	6	K122303	1.11	1.54	0.28	†	†	†	†	†
	7	K122304	1.78	0.86	0.25	†	†	†	†	†
	13	K122801	0.71	1.33	†	0.49	-0.49	†	†	†
	16	K125201	0.34	0.36	†	0.08	0.80	-1.58	0.70	†
SE	3	K154501	0.99	0.09	0.26	†	†	†	†	†
	9	K118501	0.53	1.10	†	1.27	-0.10	-1.17	†	†
	10	K154601	0.50	0.35	†	0.76	-0.76	†	†	†
	15	K154701	0.65	1.20	†	2.96	-0.39	-0.54	-2.03	†
	16	K154801	0.87	-0.82	0.23	†	†	†	†	†
	18	K120501	1.39	-0.06	0.29	†	†	†	†	†
SF	2	K124501	1.44	0.76	0.26	†	†	†	†	†
	4	K123801	0.68	0.54	†	0.52	-0.05	-0.47	†	†
	5	K123802	0.44	0.39	†	0.73	-0.73	†	†	†
	11	K155001	1.46	-0.29	0.35	†	†	†	†	†
	16	K155301	1.53	0.63	0.39	†	†	†	†	†
SG	2	K117401	1.35	0.77	0.14	†	†	†	†	†
	6	K110601	1.06	-0.79	0.32	†	†	†	†	†
	12	K110501	0.70	1.33	†	0.99	-0.99	†	†	†
	13	K121001	0.86	1.50	†	0.34	-0.34	†	†	†
	14	K1210CL	0.42	0.53	†	-0.88	1.89	-1.01	†	†
SH	1	K112801	0.95	-0.54	0.33	†	†	†	†	†
	7	K112001	1.85	0.58	0.20	†	†	†	†	†
	8	K119701	2.02	0.60	0.28	†	†	†	†	†
	14	K111601	0.68	0.19	0.17	†	†	†	†	†
	16	K155801	1.27	-0.26	0.30	†	†	†	†	†
	18	K155901	0.62	0.08	0.29	†	†	†	†	†
SI	2	K114401	1.27	0.51	0.19	†	†	†	†	†
	8	K114802	0.60	0.26	†	-0.30	0.30	†	†	†
	9	K114801	0.35	1.93	†	-1.16	2.60	-1.44	†	†
	12	K124102	0.38	0.51	†	-1.25	1.85	-0.61	†	†
SK	3	K119201	1.08	0.83	0.35	†	†	†	†	†
	10	K117001	0.54	0.98	†	0.48	-0.48	†	†	†
	11	K1170CL	0.47	1.48	†	0.03	-0.21	0.17	†	†
	12	K117005	0.82	-0.65	0.39	†	†	†	†	†
	13	K117006	1.47	1.01	0.28	†	†	†	†	†
SL	7	K123301	0.74	0.18	†	†	†	†	†	†
	12	K112601	0.70	2.02	†	0.70	-0.70	†	†	†
SJ	5	K115801	0.88	-0.01	0.28	†	†	†	†	†
	6	K1158CL	0.72	-1.92	†	0.78	-0.78	†	†	†
	7	K1564CL	0.80	0.13	†	1.11	-1.11	†	†	†
	10	K116101	0.44	1.18	†	0.89	2.06	-1.44	-1.51	†

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