Table 2.
Overview of RMT findings.
| Targeting distributions |
Measurement scale |
Sample measurement |
||||||
|---|---|---|---|---|---|---|---|---|
| Person measurements range (mean) | Item threshold rangea (%) | Disordered thresholds (%) | Item fit residual range (% outside −2.5/2.5) | Item χ2, % significant (p < 0.01)b | # of item pairs with residual correlations >0.30 | PSI | Person fit residual range (% outside −2.5/2.5) | |
| Original | ||||||||
| Physical Impact | –5.68 to 5.53 (–2.36) | 3.41 to 3.11 (58%) | 0% | –17.30 to 24.72 (80%) | 15% | One pair (r = 0.40) | 0.91 | –8.21 to 5.08 (22%, n = 1831) |
| Psychological Impact | –5.18 to 4.86 (–1.99) | –3.17 to 2.66 (58%) | 0% | –17.92 to 21.29 (89%) | 11% | 0 pairs | 0.87 | –6.54 to 3.88 (19%, n = 1549) |
| Original sub-sample (excluding EDSS ≤2.5 scores) | ||||||||
| Physical Impact | –5.81 to 5.74 (–1.18) | –3.43 to 3.38 (59%) | 0% | –10.86 to 17.12 (80%) | 10% | One pair (r = 0.31) | 0.94 | –7.97 to 4.92 (19%, n = 609) |
| Psychological Impact | –5.10 to 4.86 (–1.19) | –2.87 to 2.55 (54%) | 0% | –10.93 to 14.72 (67%) | 11% | 0 pairs | 0.89 | –6.42 to 3.63 (13%, n = 423) |
| Revised | ||||||||
| General Symptoms | –5.01 to 3.29 (–1.96) | –2.64 to 2.97 (68%) | 0% | –15.91 to 17.90 (86%) | 7% | 0 pairs | 0.87 | –7.07 to 3.86 (16%, n = 1343) |
| Psychological Impact | –5.14 to 4.74 (–2.16) | –3.62 to 3.09 (68%) | 0% | –12.96 to 12.41 (100%) | 0% | 0 pairs | 0.83 | –3.42 to 3.13 (20%, n = 1646) |
| General Limitations | –5.52 to 5.19 (–2.63) | –4.07 to 3.19 (68%) | 0% | –9.96 to 16.63 (90%) | 10% | 0 pairs | 0.87 | –5.45 to 4.00 (28%, n = 2318) |
| Revised sub-sample (excluding EDSS ≤2.5 scores) | ||||||||
| General Symptoms | –5.12 to 3.29 (–1.09) | –3.20 to 3.09 (75%) | 0% | –7.60 to 10.81 (71%) | 0% | 0 pairs | 0.90 | –7.11 to 3.85 (14%, n = 441) |
| Psychological Impact | –5.02 to 4.78 (–1.28) | –3.83 to 3.28 (67%) | 0% | –8.37 to 8.13 (60%) | 0% | 0 pairs | 0.86 | –3.39 to 3.12 (18%, n = 559) |
| General Limitations | –5.57 to 5.47 (–1.29) | –3.89 to 3.50 (67%) | 0% | –7.40 to 12.08 (90%) | 0% | 0 pairs | 0.92 | –5.60 to 4.07 (15%, n = 468) |
RMT: Rasch Measurement Theory; EDSS: Expanded Disability Status Scale; PSI = Person Separation Index; χ2 = Chi-square. aItem threshold mean is always set at 0.00 logits. bStatistical assessment on adjusted sample (n = 500) and Bonferroni correction.