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NAEP Analysis and Scaling → Estimation of NAEP Score Scales → NAEP Assessment IRT Parameters → Science Assessment IRT Parameters → IRT Parameters for the Life Science Scale, by Block and Item, Grade 8 Science National Main Assessment (Accommodations Permitted [R3]): 2000

NAEP Technical DocumentationIRT parameters for the life science scale, by block and item, grade 8 science national main assessment (accommodations permitted [R3]): 2000

Block	Item	NAEP ID	aj	bj	cj	dj1	dj2	dj3
S6	10	K031307	1.06	1.63	0.00	0.76	-0.76	†
	11	K031308	0.55	2.66	0.00	†	†	†
S8	1	K041301	0.78	-2.42	0.23	†	†	†
	2	K041302	0.92	-1.46	0.28	†	†	†
	3	K041303	0.73	-1.08	0.23	†	†	†
	4	K041304	0.58	0.02	0.12	†	†	†
	5	K041305	1.36	-0.71	0.21	†	†	†
	6	K041306	0.63	-0.74	0.00	†	†	†
	7	K041307	0.40	1.78	0.00	-0.34	0.34	†
	8	K041401	0.79	0.71	0.00	1.08	-1.08	†
	9	K041402	1.03	1.59	0.00	1.20	-1.20	†
	10	K041403	0.35	2.79	0.00	1.37	-1.37	†
S9	1	K031601	0.88	-1.71	0.23	†	†	†
	2	K031602	0.39	-0.47	0.00	0.58	-0.58	†
	3	K031603	0.69	-1.51	0.00	†	†	†
	4	K031604	0.50	0.72	0.00	†	†	†
	5	K031605	0.58	-0.46	0.39	†	†	†
	6	K031606	0.45	1.05	0.00	1.39	-1.39	†
	7	K031610	0.63	0.21	0.00	1.44	-1.44	†
	8	K031607	0.50	-0.70	0.00	0.32	0.86	-1.17
	9	K031608	0.53	1.71	0.00	1.98	-1.98	†
	10	K031609	0.51	0.51	0.00	†	†	†
	11	K031611	0.29	2.89	0.00	†	†	†
	12	K031612	0.93	-0.14	0.36	†	†	†
	13	K031613	0.64	2.34	0.00	-0.93	0.93	†
S10	1	K092301	0.87	-1.28	0.24	†	†	†
	2	K098801	1.16	-0.03	0.21	†	†	†
	8	K090601	1.01	0.24	0.18	†	†	†
	17	K092901	0.59	1.27	0.18	†	†	†
	18	K096101	0.79	1.30	0.00	1.10	-1.10	†
	19	K090701	0.28	0.98	0.28	†	†	†
	20	K098901	0.48	0.15	0.19	†	†	†
	5	K099001	0.48	-0.33	0.00	1.68	-1.68	†
S11	6	K043001	0.27	3.52	0.00	0.92	-0.92	†
	12	K043401	0.30	-0.39	0.24	†	†	†
S12	8	K047501	0.90	2.41	0.35	†	†	†
	10	K047701	0.81	2.80	0.15	†	†	†
	11	K047801	1.04	1.11	0.17	†	†	†
	13	K048001	0.85	0.96	0.00	1.82	-1.82	†
	14	K048101	0.50	1.55	0.00	0.46	-1.22	0.76
	15	K048102	0.69	4.25	0.00	1.61	-1.61	†
	16	K048103	0.49	0.88	0.00	†	†	†
S13	3	K048401	0.63	0.72	0.23	†	†	†
	8	K048901	0.49	0.39	0.00	0.39	-0.39	†
	11	K049201	0.22	0.50	0.24	†	†	†
	12	K049301	0.31	4.41	0.00	†	†	†
S14	2	K035501	0.52	-1.86	0.24	†	†	†
	6	K035901	0.57	1.03	0.00	†	†	†
	12	K036501	1.20	0.98	0.36	†	†	†
	14	K036701	0.40	2.86	0.00	-0.59	0.59	†
	15	K036801	0.51	1.40	0.00	-0.50	0.50	†
S15	2	K037101	0.26	-2.76	0.24	†	†	†
	3	K037201	0.67	-1.15	0.23	†	†	†
	12	K038001	0.76	1.80	0.23	†	†	†
	13	K038002	1.22	1.24	0.16	†	†	†
	14	K038101	0.65	2.45	0.00	†	†	†
S10	1	K093001	0.73	-1.36	0.24	†	†	†
	12	K090201	0.76	-0.29	0.23	†	†	†
	13	K092801	0.53	3.62	0.00	†	†	†
	17	K091601	0.64	1.72	0.17	†	†	†
	18	K094901	0.47	3.52	0.00	1.69	-1.69	†
	19	K095001	0.60	0.42	0.19	†	†	†
	20	K091201	1.42	1.00	0.21	†	†	†
S21	1	K045201	0.61	-1.72	0.25	†	†	†
	2	K045301	0.34	3.20	0.00	†	†	†
	5	K045601	0.59	1.67	0.00	0.98	-0.98	†
	9	K046001	0.40	0.38	0.15	†	†	†
	12	K046301	0.30	2.03	0.00	3.45	-3.45	†
	13	K046401	0.63	1.92	0.00	†	†	†
	16	K046701	0.55	1.14	0.00	2.15	-1.46	-0.69
† Not applicable; the number of item parameters estimated depends upon the IRT model used for scaling. 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 is the category threshold parameter for category i. The c-parameter value is exactly zero for items scaled with the two-parameter logistic model or the generalized partial credit model. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2000 Science Assessment.

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