NAEP Analysis and Scaling → Estimation of NAEP Score Scales → NAEP Assessment IRT Parameters → Mathematics Long-Term Trend Assessment IRT Parameters → IRT Parameters, Age 9 Mathematics Long-Term Trend Assessment, by Item and Block: 2008

NAEP Technical DocumentationIRT parameters, age 9 mathematics long-term trend assessment, by item and block: 2008

Block	Item	NAEP ID	aj	bj	cj
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. The c parameter value is exactly zero for items scaled with the two-parameter logistic model. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2008 Mathematics Long-Term Trend Assessment.
M1	1	N291601	0.83	-0.60	0.09
	2	N291701	0.81	-1.13	0.26
	3	N291801	1.65	2.06	0.14
	4	N291901	0.40	1.43	0.17
	5	N292001	0.65	-0.80	0.08
	6	N292101	1.07	-0.86	†
	7	N292201	0.80	0.92	0.18
	8	N292301	0.76	0.42	0.35
	9	N292401	0.58	-0.39	†
	10	N292501	1.42	0.98	0.43
	11	N292601	1.37	0.08	0.15
	12	N292701	1.06	-0.93	0.30
	13	N292801	0.84	-1.33	0.28
	14	N292901	1.36	-0.79	0.14
	15	N293001	0.87	-0.53	†
	16	N293101	1.10	-2.03	0.11
	17	N293201	1.24	0.69	0.18
	18	N293301	0.85	-1.00	†
	19	N293401	0.96	-1.16	0.19
	20	N293501	0.70	-0.88	†
	21	N293601	1.46	0.84	0.19
	22	N293701	1.66	0.18	0.10
	23	N293801	1.39	0.64	0.20
M2	1	N293901	1.09	-1.37	0.10
	2	N294001	0.82	-2.57	0.13
	3	N294101	0.90	-1.38	0.32
	4	N294201	0.80	-2.93	†
	5	N294301	0.98	-0.96	†
	6	N294401	0.86	-0.86	0.17
	7	N294501	0.93	-0.68	0.10
	8	N294601	1.24	0.00	0.19
	9	N294701	0.46	-2.48	0.14
	10	N294801	1.68	1.58	0.14
	11	N294901	0.75	0.08	0.24
	12	N295001	0.68	-2.09	0.15
	13	N295101	1.15	-0.28	0.19
	14	N295201	1.19	-0.18	0.19
	15	N295301	1.05	-1.20	†
	16	N295401	0.99	-0.55	†
	17	N295501	1.33	0.27	0.20
	18	N295601	0.93	-1.30	0.17
	19	N295701	1.16	0.73	†
	20	N295801	1.17	0.33	0.33
	21	N295901	1.36	1.27	0.07
	22	N296001	1.09	0.69	0.31
	23	N296101	1.06	0.88	0.23
M3	1	N322001	0.64	-3.07	0.23
	2	N322101	0.47	-0.69	0.18
	3	N322201	0.93	-0.59	0.18
	4	N322301	0.91	-1.15	0.32
	5	N322401	0.77	-0.14	†
	6	N322501	1.77	1.00	0.14
	7	N322601	0.84	-1.29	0.12
	8	N322602	0.93	1.57	0.08
	9	N322701	0.25	0.36	0.23
	10	N322801	0.25	-3.41	0.25
	11	N322901	0.59	-0.73	0.20
	12	N323001	0.85	-0.94	0.10
	13	N323101	1.12	-0.19	†
	14	N323201	1.02	-1.40	0.24
	15	N323301	1.31	0.76	0.22
	16	N323401	0.95	-1.85	0.28
	17	N323501	1.01	1.46	0.44
	18	N323601	0.80	0.12	0.28
	19	N323701	0.94	-0.48	†
	20	N323801	1.23	0.65	0.14
	21	N323901	0.98	-0.60	†
	22	N324001	1.05	-0.48	†
M4	1	N312401	1.06	-2.03	0.16
	2	N312501	1.59	-0.63	0.28
	3	N312601	0.65	-1.49	0.20
	4	N312701	0.99	-1.97	0.24
	5	N312702	0.76	-2.03	0.21
	6	N312801	0.76	-1.46	0.37
	7	N312901	0.98	-1.21	†
	8	N313001	0.66	-1.38	†
	9	N313101	0.90	-0.97	†
	10	N313102	0.90	0.00	†
	11	N313103	0.85	-0.18	†
	12	N313201	0.44	-0.94	0.19
	13	N313301	1.13	-2.04	0.20
	14	N313302	0.57	-1.81	0.09
	15	N313303	0.99	-0.32	0.12
	16	N313401	0.77	-0.84	0.12
	17	N313501	0.61	-1.45	0.08
	18	N313502	1.06	0.23	0.15
	19	N313503	1.26	-0.63	0.11
	20	N313601	1.66	0.60	0.43
	21	N313701	0.98	-0.82	†
	22	N313702	1.20	0.52	†
	23	N313801	0.90	-0.52	†
	24	N313901	0.82	-0.70	†
	25	N314001	1.54	1.06	0.28
	26	N314101	1.00	1.57	0.09
M5	1	N287401	1.04	-0.05	0.15
	2	N287501	1.31	-0.72	0.13
	3	N287601	1.12	0.82	†
	4	N287701	0.76	-1.52	0.31
	5	N287801	0.77	-2.08	0.12
	6	N287901	0.81	-1.72	0.20
	7	N288001	1.18	-0.20	0.16
	8	N288101	0.64	-0.37	†
	9	N288201	1.37	1.18	0.24
	10	N288301	0.74	-1.87	0.17
	11	N288401	1.15	-0.40	0.39
	12	N288501	1.09	-0.59	†
	13	N288601	1.25	-0.08	0.12
	14	N288701	1.07	-1.22	0.24
	15	N288801	1.49	0.64	0.27
	16	N288901	0.93	-0.32	0.22
	17	N289001	1.31	0.60	0.20
	18	N289101	1.40	0.39	0.12
	19	N289201	1.21	-0.39	†
	20	N289301	1.19	1.74	0.25
	21	N289401	0.64	-0.20	0.34
M6	1	N289501	0.47	-1.63	0.23
	2	N289601	1.12	-0.75	0.48
	3	N289701	1.10	-0.72	†
	4	N289801	0.98	-1.28	0.24
	5	N289901	0.60	-2.31	†
	6	N290001	0.73	-1.00	0.24
	7	N290101	0.85	0.11	†
	8	N290201	1.18	0.02	0.13
	9	N290301	2.25	1.62	0.14
	10	N290401	0.62	-0.41	0.13
	11	N290501	0.54	-1.37	0.31
	12	N290601	1.25	-0.13	0.45
	13	N290701	0.32	-3.93	†
	14	N290801	1.28	0.15	0.12
	15	N2909CL	0.46	4.25	†
	16	N291101	0.85	-0.17	0.30
	17	N291201	1.49	-0.10	0.18
	18	N291301	0.99	1.53	0.36
	19	N291401	0.73	-0.08	0.25
	20	N291501	0.47	1.89	†

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