Validation of the Headache Impact Test (HIT-6) in patients with chronic migraine

Table 3 Tests of measurement invariance using multi-group confirmatory factor analysis

	Model fit			Model comparison
Parameter constraints	TLI	CFI	RMSEA	∆CFI	∆RMSEA	Chi-square for nested model comparison
Measurement Invariance Across Studies
None - Configural Model	0.979	0.978	0.086	—	—	—
Thresholds	0.990	0.980	0.059	0.002	−0.027	22.754 (DF = 15); (P = 0.0895)
Thresholds and loadings	0.992	0.982	0.052	0.002	−0.007	3.579 (DF = 4); (P = 0.4659)
Thresholds, loadings, and residual variances	0.993	0.982	0.050	0.000	−0.002	9.655 (DF = 6); (P = 0.1399)

Values under the column heading “Model Comparison” refer to the comparison of the model in the corresponding row and the model in the preceding row.
CFI = comparative fit index; ΔCFI = change in CFI; DF = degrees of freedom; RMSEA = root mean square error of approximation; ΔRMSEA = change in RMSEA; TLI = Tucker-Lewis Index.

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