Table 2.
Summary of psychometric and Rasch analysis used to select items per dimension
| Psychometric analysis | Rasch analysis | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
| |||||||||||||
| Items | Item summary | % response at floor (very much) | % response at ceiling (not at all) | % missing data | Correlation with domain score | SRM | Item range | Residual | Item level chi-sq P-value | Spread at logit zero | Disordered | DIF characteristic | Poorly fitting item in Rasch model (Chi-sq P-value<0.01) |
| Physical and role functioning and pain | |||||||||||||
| 1 | Trouble doing strenuous activities | 28.5 | 14.4 | 0.6 | −0.869 | −0.206 | Sex | ||||||
| 2 | Trouble taking a long walk | 26.9 | 16.9 | 1.1 | −0.896 | −0.195 | −2.576 to 0.516 | −1.540 | 0.385 | 0.93 to 0.37 | |||
| 3 | Trouble taking a short walk | 8.1 | 46.7 | 1.7 | −0.844 | −0.235 | Sex | ||||||
| 4 | Need to stay in bed or a chair during the day | 9.3 | 36 | 1.4 | −0.788 | −0.289 | −1.158 to 2.385 | 0.874 | 0.120 | 0.76 to 0.08 | |||
| 5 | Need help with eating, dressing, washing or using the toilet | 4.1 | 72.8 | 0.6 | −0.575 | −0.313 | 1.220 to 2.584 | −0.678 | 0.083 | 0.23 to 0.07 | |||
| 6 | Limited in doing your work or daily activities | 18.5 | 25.8 | 1.5 | −0.953 | −0.259 | Yes | ||||||
| 7 | Limited in pursuing hobbies or other leisure time activities | 17.9 | 30.1 | 1.2 | −0.954 | −0.237 | −1.526 to −1.192 | −0.629 | 0.600 | 0.82 to 0.23 | |||
| 9 | Pain | 20 | 20.2 | 0.9 | 0.926 | −0.499 | −2.176 to 1.004 | 4.685 | 0.075 | 0.90 to 0.27 | |||
| 19 | Pain interfered with daily activities | 20 | 30.4 | 0.5 | 0.936 | −0.432 | −1.427 to 0.987 | −0.844 | 0.138 | 0.81 to 0.27 | |||
| Social functioning | |||||||||||||
| 26 | Physical condition or medical treatment interfered with family life | 8.7 | 49.2 | 0.8 | −0.899 | −0.085 | −1.247 to 2.013 | 1.146 | 0.175 | 0.78 to 0.12 | |||
| 27 | Physical condition or medical treatment interfered with social life | 12.8 | 41.8 | 0.6 | −0.942 | −0.090 | −1.869 to 1.144 | 0.555 | 0.345 | 0.87 to 0.24 | |||
| Emotional functioning | |||||||||||||
| 21 | Feel tense | 6.6 | 37.7 | 0.9 | −0.834 | −0.264 | Age | ||||||
| 22 | Worried | 12.8 | 26.0 | 0.2 | −0.860 | −0.477 | Sex | ||||||
| 23 | Feel irritable | 4.3 | 44.3 | 0.5 | −0.776 | −0.223 | −1.546 to 2.740 | 3.912 | 0.442 | 0.82 to 0.06 | |||
| 24 | Feel depressed | 7.8 | 41.5 | 0.8 | −0.834 | −0.330 | −1.696 to 2.017 | −0.742 | 0.232 | 0.85 to 0.12 | |||
| Digestion | |||||||||||||
| 13 | Lacked appetite | 8.9 | 48.9 | 0.5 | No domain | −0.348 | −1.349 to −0.314 | −2.244 | 0.027 | 0.79 to 0.58 | |||
| 14 | Felt nauseated | 2.4 | 73.9 | 0.3 | No domain | −0.124 | Yes | ||||||
| 15 | Vomited | 1.2 | 87.9 | 0.3 | No domain | −0.046 | Yes | Sex | |||||
| 16 | Constipated | 7.3 | 52.7 | 0.5 | No domain | −0.225 | −1.258 to −0.449 | −1.220 | 0.231 | 0.78 to 0.61 | |||
| 17 | Had diarrhoea | 0.8 | 79.5 | 0.9 | No domain | 0.058 | −0.081 to 1.083 | 1.029 | 0.027 | 0.52 to 0.25 | |||
| Fatigue and trouble sleeping | |||||||||||||
| 10 | Needed to rest | 15.9 | 14 | 1.4 | No domain | −0.326 | −3.113 to 2.212 | 1.409 | 0.881 | 0.96 to 0.10 | |||
| 11 | Trouble sleeping | 10.1 | 41.4 | 0.2 | No domain | −0.276 | Yes | ||||||
| 12 | Felt weak | 12.7 | 22.6 | 0.6 | No domain | −0.296 | −2.155 to 2.641 | −0.433 | 0.043 | 0.90 to 0.07 | |||
| 18 | Tired | 12.8 | 15.9 | 0.3 | No domain | −0.245 | −2.933 to 2.805 | −0.727 | 0.540 | 0.95 to 0.06 | |||
Note: DIF by sex is split male/female and DIF by age is split <65/65+.