Table 2 Model fit statistics for original and revised DASS-21 scales
From: Rasch model analysis of the Depression, Anxiety and Stress Scales (DASS)
Action | Analysis | Overall model fit | Item Fit Resid Mean (SD) | Person Fit Resid Mean (SD) | PSI | % signif t-tests |
|---|---|---|---|---|---|---|
DASS-21-Depression | Â | Â | Â | Â | Â | Â |
1. Original scale | 1 | χ2 = 86.68 p < .001 | -0.73 (2.60) | -0.34 (0.90) | 0.87 |  |
2. Removal of item 5 | 2 | χ2 = 38.41 p = .03 | -0.21 (0.84) | -0.34 (0.93) | 0.89 | 1.45% |
DASS-21-Anxiety | Â | Â | Â | Â | Â | Â |
3. Original scale | 3 | χ2 = 69.76 p < .001 | -0.69 (1.51) | -0.34 (0.95) | 0.76 |  |
4. Removal of item 2 | 4 | χ2 = 40.57 p = .02 | -0.52 (0.89) | -0.34 (1.12) | 0.77 | 2.77% |
DASS-21-Stress | Â | Â | Â | Â | Â | Â |
5. Original scale | 5 | χ2 = 57.47 p < .001 | -0.29 (1.69) | -0.40 (1.30) | 0.84 |  |
6. Removal of item 11 | 6 | χ2 = 42.09 p = .01 | -0.27 (1.36) | -0.40 (1.22) | 0.80 | 3.36% |
DASS-21-Total | Â | Â | Â | Â | Â | Â |
7. Original scale | 7 | χ2 = 236.4 p < .001 | -0.46 (2.33) | -0.30 (1.27) | 0.90 |  |
8. Removal of items 1,2,5,19,14 | 8 | χ2 = 100.19 p = .003 | -0.46 (1.49) | -0.32 (1.21) | 0.90 | 11.61% CI:9–14% |
DASS-21-Anxiety/Stress | Â | Â | Â | Â | Â | Â |
9. Original scale | 9 | χ2 = 159.20 p < .001 | -0.47 (2.18) | -0.31 (1.15) | 0.87 |  |
10. Removal of items 2, 11, 15 | 10 | χ2 = 60.90 p = .046 | -0.55 (1.27) | -0.36 (1.08) | 0.84 | 3.07% |