Irritable bowel syndrome-specific health-related quality of life instrument: development and psychometric evaluation

Table 3 Tests for multigroup invariance across the IBS-subtype groups

	χ ² (df)	χ ²/df	RMSEA (90 % CI)	Comparison	∆χ ² (∆df)	p
Model 1^a	704.92 (388)	1.81	0.06 (0.05–0.06)	-	-	-
Model 2^b	743.48 (424)	1.75	0.05 (0.05–0.06)	Model 1 vs. Model 2	38.57 (36)	0.354
Model 3^c	775.72 (454)	1.71	0.05 (0.04–0.06)	Model 2 vs. Model 3	32.24 (30)	0.357
Model 4^d	834.67 (505)	1.65	0.05 (0.04–0.06)	Model 3 vs. Model 4	58.95 (51)	0.207

^aConfigural Model: No equality constraints imposed
^bAll factor loadings constrained equal
^cAll factor loadings and covariances among 4 factors constrained equal
^dAll factor loadings, covariances among 4 factors, and error variance constrained equal
∆χ ²= difference in χ ² values between models
∆df = difference in number of degrees of freedom between models

ISSN: 1477-7525