Table 1.
Scoring for final item selection
| Category | Cut-off | Scores |
|---|---|---|
| Perceived weekly frequency of activities (“often” and “sometimes”) | >13 times | 2 |
| 6–12 times | 1 | |
| <6 times | 0 | |
| Item-to-total correlation | 0.6–0.9 | 2 |
| 0.4–0.59 | 1 | |
| <0.4 or >0.9 | 0 | |
| Principal component analysis | Loading on one factor >0.5 | 2 |
| Loading on two or no factor >0.5 | 0 | |
| Rasch analysis (item fit) | 0.5–1.5 | 2 |
| >1.5 to 2 | 1 | |
| >2 or <0.5 | 0 | |
| Floor or ceiling effect | <85 % | 2 |
| >85 % | 0 | |
| Experts’ opinion on relevance of SFS item (“yes”) | All experts | 1 |
| 3 out of 4 | 0.75 | |
| 2 out of 4 | 0.5 | |
| 1 out of 4 | 0.25 | |
| None | 0 |
SFS spinal function sort