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Table 2 Fit indices of confirmatory factor analyses in different Insomnia Severity Index factor models (n = 249)

From: Preliminary validation of the insomnia severity index in Danish outpatients with a medical condition

Model Chi2 p-value RMSEA CFI TLI SRMR AIC BIC p-value*
Threshold for fit indices None > 0.05 < 0.08 ≥0.90 ≥0.95 < 0.08 Lowest value Lowest value < 0.05
Model 1.
One factor: All 7 items
87.030 < 0.001 0.145 0.931 0.896 0.048 4285.162 4359.028 ref
Model 2.
Two factors:
Subscale 1: 1, 2, 3, 4
Subscale 2: 5, 6, 7
40.577 < 0.001 0.092 0.974 0.958 0.033 4240.709 4318.093 1.0
Model 3.
Two factors:
Subscale 1: 1, 2, 3
Subscale 2: 4, 5, 6, 7
67.746 < 0.001 0.130 0.948 0.916 0.042 4267.877 4345.261 1.0
Model 4.
Three factors:
Subscale 1: 1, 2, 3
Subscale 2: 1, 4, 7
Subscale 3: 5, 6, 7
26.497 0.002 0.089 0.983 0.961 0.025 4234.629 4326.083 1.0
  1. Bold text for the best fitted value for the indices
  2. RMSEA Root Mean Square Error of Approximation, CFI Comparative Fit Index, TLI Tucker–Lewis fit Index, SRMR Standardized Root Mean Square Residual, AIC Akaike’s Information Criterion, BIC Bayesian Information Criterion
  3. *Likelihood ratio test