Evaluating the Longitudinal Item and Category Stability of the SF-36 Full and Summary Scales Using Rasch Analysis

Table 14

SF-36 mental health scale Rasch analysis Infit and Outfit statistics for six waves of data collection.

	Wave 1				Wave 2				Wave 3
SF36 ITEM	Infit		Outfit		Infit		Outfit		Infit		Outfit
	MNSQ	ZSTD	MNSQ	ZSTD	MNSQ	ZSTD	MNSQ	ZSTD	MNSQ	ZSTD	MNSQ	ZSTD
17:Q5A	0.29	-9.9	0.32	-9.9	0.26	-9.9	0.28	-9.9	0.30	-9.9	0.32	-9.9
18:Q5B	0.43	-9.9	0.46	-9.9	0.43	-9.9	0.46	-9.9	0.48	-9.9	0.50	-9.9
19:Q5C	0.31	-9.9	0.34	-9.9	0.29	-9.9	0.31	-9.9	0.32	-9.9	0.34	-9.9
20:Q6	2.64	9.9	2.87	9.9	2.91	9.9	3.06	9.9	2.54	9.9	2.74	9.9
23:Q9A	1.08	7.7	1.15	9.9	1.03	3.2	1.12	9.9	1.04	3.5	1.09	6.7
24:Q9B	1.25	9.9	1.17	9.9	1.40	9.9	1.29	9.9	1.41	9.9	1.31	9.9
25:Q9C	1.44	9.9	1.30	9.9	1.59	9.9	1.39	9.9	1.51	9.9	1.33	9.9
26:Q9D	1.22	9.9	1.33	9.9	1.14	9.9	1.28	9.9	1.10	7.1	1.19	9.9
27:Q9E	1.12	9.9	1.17	9.9	1.08	7.8	1.12	9.9	1.07	5.3	1.08	6.3
28:Q9F	0.90	-6.6	0.88	-8.3	1.02	1.0	0.98	-0.9	0.96	-2.0	0.93	-3.6
29:Q9G	0.88	-9.9	0.87	-9.9	0.90	-7.4	0.89	-7.8	0.88	-7.8	0.87	-8.2
30:Q9H	1.22	9.9	1.29	9.9	1.15	8.5	1.24	9.9	1.09	4.6	1.16	7.9
31:Q9I	0.72	-9.9	0.73	-9.9	0.76	-9.9	0.77	-9.9	0.73	-9.9	0.74	-9.9
32:Q10	0.72	-9.9	0.77	-9.9	0.78	-9.9	0.81	-9.9	0.87	-9.9	0.91	-6.8
	Wave 4				Wave 5				Wave 6
SF36 ITEM	Infit		Outfit		Infit		Outfit		Infit		Outfit
	MNSQ	ZSTD	MNSQ	ZSTD	MNSQ	ZSTD	MNSQ	ZSTD	MNSQ	ZSTD	MNSQ	ZSTD
17:Q5A	0.31	-9.9	0.34	-9.9	0.34	-9.9	0.37	-9.9	0.36	-9.9	0.39	-9.9
18:Q5B	0.50	-9.9	0.52	-9.9	0.52	-9.9	0.54	-9.9	0.53	-9.9	0.55	-9.9
19:Q5C	0.34	-9.9	0.36	-9.9	0.37	-9.9	0.39	-9.9	0.38	-9.9	0.41	-9.9
20:Q6	2.16	9.9	2.33	9.9	1.96	9.9	2.15	9.9	1.91	9.9	2.07	9.9
23:Q9A	1.04	2.7	1.07	5.3	1.02	1.7	1.05	3.4	1.03	1.8	1.04	2.2
24:Q9B	1.37	9.9	1.25	9.9	1.36	9.9	1.25	9.5	1.33	9.9	1.25	8.3
25:Q9C	1.50	9.9	1.36	9.9	1.51	9.9	1.36	9.9	1.42	9.9	1.32	9.1
26:Q9D	1.15	9.3	1.23	9.9	1.16	8.7	1.26	9.9	1.13	6.2	1.20	8.8
27:Q9E	1.11	7.9	1.11	8.0	1.08	5.1	1.08	4.8	1.10	5.2	1.09	4.4
28:Q9F	0.97	-1.6	0.94	-3.2	0.95	-2.2	0.91	-4.2	0.91	-3.5	0.89	-4.4
29:Q9G	0.87	-8.1	0.86	-8.5	0.84	-9.2	0.83	-9.7	0.85	-7.3	0.84	-7.8
30:Q9H	1.12	5.6	1.16	7.3	1.13	5.8	1.22	9.3	1.09	3.6	1.15	5.3
31:Q9I	0.76	-9.9	0.77	-9.9	0.76	-9.9	0.77	-9.9	0.76	-9.9	0.78	-9.9
32:Q10	0.86	-9.9	0.91	-6.9	0.90	-6.3	0.94	-3.9	0.96	-2.4	1.00	0.2

Notes. MNSQ = mean square residual fit statistic; ZSTD: standardized mean square residual fit statistic; values in italic for Infit or Outfit MnSq > 1.34; values underlined for Infit or Outfit MnSq < 0.64.