Developing a dementia-specific health state classification system for a new preference-based instrument AD-5D

Table 4 Rasch analysis results by individual items

		Response category ordering	Item range		Fit residuals	χ2 p-value	DIF
Interpersonal environment
Item 4	Living situation	Ordered	−1.636	1.879	1.633	0.169	No DIF
Item 6	Family	Ordered	−1.428	2.012	−0.311	0.597	Age
Item 7	Staff	Ordered	−1.373	1.667	−1.481	0.247	No DIF
Item 8	Friends	Ordered	−1.634	1.932	0.207	0.977	No DIF
Item 12	Live with others	Ordered	−1.827	2.318	0.223	0.738	Age
Item 13	Make choices	Ordered	−1.978	2.467	0.113	0.951	ESL
Physical health
Item 1	Physical health	Ordered	−1.183	1.691	0.758	0.441	No DIF
Item 2	Energy	Ordered	−1.282	1.801	0.574	0.288	Gender
Self-functioning
Item 9	Keep busy	Ordered	−2.291	2.588	0.000	0.934	Age
Item 10	Do fun things	Ordered	−1.958	2.563	0.029	0.725	No DIF
Item 11	Self-care	Disordered (poor/fair)	-	-	-	-	-

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