| MEASUREMENT PROPERTIES | |
| Limitations | |
| Observations | |
| 1. RELIABILITY | |
| A. Internal Consistency | Tested |
| Cronbach's (Describe) |
Cronbach’s α reliability coefficients for the FDI are high (α = 0.79-0.92) (17,32,33). The mean interim correlation is 0.38 |
| B. Reliability intraobserver or test-retest | Tested |
| Continuous scores: intraclass correlation coefficient (ICC) Dichotomus: Cohen kappa (Describe) |
Test-retest correlations are high at the 2-week (r = 0.80; P < 0.001), 6-week (r = 0.70; P < 0.001), and 6-month follow-up (r = 0.63; P < 0.001) |
| C. Reliability interobserver or Measurement error | Not Tested |
| Standard error of measurement (SEM), smallest detectable change (SDC) or Limits of agreement (LoA) (Describe) |
|
| 2. VALIDITY | |
| A. Content validity: face validity | Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
The FDI has a Flesch reading ease of 89.7 and a Flesch-Kincaid grade level of 3.2 |
| B. Construct Validity: Structural validity |
Not Tested |
| Hypotheses-testing | Tested |
| Cross-cultural validity | Not Tested |
| Brief Description | |
| C. Criterion validity | Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
Concurrent validity was assessed by calculating correlation on the FDI with school absences, a common proxy for child disability). Scores on the FDI significantly correlated (r = 0.52; P < 0.001) with the number of school days missed in the previous 3 months. Discriminant validity was assessed by examining whether the FDI could discriminate between diagnostic groups. The FDI discriminated between the three groups (F2,97 = 26.40; P < 0.001). Post hoc analyses indicated significantly higher FDI scores for adolescents with abdominal pain conditions compared with healthy controls. |