Is the Patient Activation Measure a valid measure of osteoarthritis self-management attitudes and capabilities? Results of a Rasch analysis

Table 3 Item fit statistics for the PAM-13

PAM items (in order of difficulty)	Difficulty calibration (logits)	Infit Mean squared	Outfit Mean squared
1	−1.52	1.21	1.13
2	−1.50	1.58	1.97
4	−1.07	1.27	1.16
6	−0.75	0.80	0.75
3	−0.75	0.95	0.89
7	−0.55	0.95	1.04
5	−0.40	0.85	0.80
8	0.11	0.74	0.70
13	1.14	1.12	1.44
9	1.17	0.91	0.95
10	1.19	0.96	0.97
12	1.23	0.96	0.96
11	1.68	0.93	1.29

Note: Results in bold indicate values that are beyond the ideal cutoffs for infit and outfit statistics (i.e. Msq of 0.5–1.5)

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