| MEASUREMENT PROPERTIES | |
| Limitations | >=5 European languages (English) |
| Observations | |
| 1. RELIABILITY | |
| A. Internal Consistency | Tested |
| Cronbach's (Describe) |
High internal consistency (Cronbach's =0.91) |
| B. Reliability intraobserver or test-retest | Tested |
| Continuous scores: intraclass correlation coefficient (ICC) Dichotomus: Cohen kappa (Describe) |
Intraclass correlation coefficient: 0.97 |
| C. Reliability interobserver or Measurement error | Tested |
| Standard error of measurement (SEM), smallest detectable change (SDC) or Limits of agreement (LoA) (Describe) |
SEM: 2.76 |
| 2. VALIDITY | |
| A. Content validity: face validity | Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
Each question’s final wording was achieved through peer panel consensus, then given to two focus groups for feedback and relevance. Missing responses were less than 1.5% and readability was graded=7, reading ease=64%. |
| B. Construct Validity: Structural validity |
Tested |
| Hypotheses-testing | Not Tested |
| Cross-cultural validity | Tested |
| Brief Description |
A unidimensional structure was indicated for SFI as the three a priori criteria were met with second point screeplot inflection and one eigenvalue of more than 1.0, where variance was greater than 10% (33.4%). The SFI had six more factors with eigenvalues of more than 1.0 but with variance of lower than 10% that accounted for 30.5%, and four factors with eigenvalues between 0.5 and 1.0, with the remaining factors all below a 0.5 eigenvalue. |
| C. Criterion validity | Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
The Spine Functional Index (SFI) was preferred in criterion validity to the Functional Rating Index (FRI) with Criterion validity high (Pearson r=0.85) between the SFI and FRI scores. |