Table 2.
Fit statistics for the IRT Models for SDE and IM polytomous scoring.
| Model | Polytomous GRM | |||||
|---|---|---|---|---|---|---|
| SDE | IM | |||||
| One factor | Two factors | Modified two factor | One factor | Two factors | Modified two factor | |
| −2LL | −20222.100 | −20085.330 | −18215.880 | −19840.54 | −19819.54 | −19921.85 |
| M2 (df) | 234.855973 (70)* | 192.4555328 (69)* | 96.093184 (44)* | 234.855973 (70)* | 192.4555328 (69)* | 311.5418137 (72)* |
| RMSEA2 (CI.90%) | .072 (.064, .081) | .055 (.045, .064) | .045 (.033, .058) | .064 (.055, .073) | .056 (.046, .065) | .076 (.067, .085) |
| SRMSR | .067 | .063 | .059 | .067 | .063 | .098 |
| AIC | 40724.19 | 40452.67 | 36685.77 | 39961.09 | 39921.08 | 40119.7 |
| BIC | 41334.29 | 41067.12 | 37239.21 | 40571.18 | 40535.53 | 40721.08 |
| saBIC | 40889.85 | 40619.51 | 36836.00 | 40126.74 | 40087.92 | 40282.99 |
| Estimated parameters | 140 | 141 | 127 | 140 | 141 | 138 |
| −2LLchange | 136.77 (1), p < .001 | 21.00 (1), p < .001 | ||||
| 1869.450 (14), p < .001 | 102.31 (3), p < .001 | |||||
−2LL = log-likelihood test. RMSEA2, bivariate root mean square error of approximation; SRMSR, Standardized Root Mean Square Residual; AIC, Akaike information criterion; BIC, Bayesian information criterion; saBIC, sample size adjusted BIC. Bold indicates when model fit index indicates the better fitting model. The one-factor scale represents the unidimensional construct SDE or IM, two factors indicate items of SDE and IM divided in Denial and Enhancement based on reversed and non-reversed items, Modified two-factor model is a two-factor model after correcting for possible local dependence and item misfit (S-X2). *Statistically significant model misfit at p < .05. Bold indicates when model fit index indicates the better fitting model.