| MEASUREMENT PROPERTIES | |
| Limitations | |
| Observations | |
| 1. RELIABILITY | |
| A. Internal Consistency | Tested |
| Cronbach's (Describe) |
Internal consistency was analyzed in the original study of 92 patients from a foot arthritis clinic at a Veterans Health Administration hospital. A Rasch analysis of the FFI‐R total score found a person reliability of 0.96 and an item reliability of 0.93. The item reliabilities for the subscales were as follows: pain and stiffness, 0.93; disability, 0.92; activity limitation, 0.90; and social/emotional issues, 0.84. For the short form FFI‐R, the person reliability was 0.95, which suggests the total score of the short form FFI‐R is similar to the total score for the long form FFI‐R. The test‐retest reliability has not been determined for the FFI‐R. |
| B. Reliability intraobserver or test-retest | Not Tested |
| Continuous scores: intraclass correlation coefficient (ICC) Dichotomus: Cohen kappa (Describe) |
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| 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 | Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
Content validity of the FFI‐R was evaluated by using the original FFI, a literature review, interviews with foot specialists, reviews by foot specialists in a focus group, interviews with patients about their experiences, and reactions to completing a draft of the FFI‐R . |
| B. Construct Validity: Structural validity |
Tested |
| Hypotheses-testing | Tested |
| Cross-cultural validity | Tested |
| Brief Description |
Construct validity has been evaluated by using Rasch item maps and the correlation with the time taken to walk 50 ft. Rasch item maps found that items of low‐severity foot problems (eg, standing on tip toes) were found at the bottom (low disability) of the item hierarchy. Conversely, items of high severity (eg, being bed‐bound) were found at the top (high disability) of the item hierarchy. |
| C. Criterion validity | Not Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
Criterion validity has not been evaluated because of the absence of a gold standard measure of foot pain or function. |