| MEASUREMENT PROPERTIES | |
| Limitations | <5 European languages (English) |
| Observations | |
| 1. RELIABILITY | |
| A. Internal Consistency | Tested |
| Cronbach's (Describe) |
The Cronbach’s alpha was estimated to be 0.83. |
| B. Reliability intraobserver or test-retest | Tested |
| Continuous scores: intraclass correlation coefficient (ICC) Dichotomus: Cohen kappa (Describe) |
Mean difference between measures: -0.53 points (test: 40.4 +/-6.1; retest 39.9 +/- 6.4). The intraclass correlation coefficient was found to be 0.92. |
| C. Reliability interobserver or Measurement error | Not Tested |
| Standard error of measurement (SEM), smallest detectable change (SDC) or Limits of agreement (LoA) (Describe) |
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| 2. VALIDITY | |
| A. Content validity: face validity | Not Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
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| B. Construct Validity: Structural validity |
Tested |
| Hypotheses-testing | Tested |
| Cross-cultural validity | Tested |
| Brief Description |
Exploratory factor analysis supported validity of the one-factor structure, however, confirmatory factor analysis suggested better properties in relation to a two-factor structure (χ2 = 59.52; CFI = 0.98; TLI = 0.96; RMSEA = 0.06). The two factors could be broadly described as "subjectively estimated work ability" and "ill-health-related ability". |
| C. Criterion validity | Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
Analyses of correlations showed predictive power of WAI as strong and consistent with expected directions. It turned out that the higher WAI, the higher individual’s General Health Index; the lower burnout due to work; and the lower van Korff disability index. In the total sample mentioned, coefficients amounted to r = -0.62, -0.54 and -0.52 (respectively). Criterion validity analysis showed that this instrument and all dimensions of the Iranian version of SF-36 were correlated significantly. Item correlation corrective for overlap showed the items tests had a good correlation except for one. |