Table 3 Data quality, scaling assumptions, targeting, reliability and validity
CDIP Scale | Head and Neck Symptoms (6 items) | Pain and Discomfort (5 items) | Upper Limb Activities (9 items) | Walking (9 items) | Sleep (4 items) | Annoyance (8 items) | Mood (7 items) | Psycho- social Functioning (10 items) |
|---|---|---|---|---|---|---|---|---|
Psychometric property | ||||||||
Data quality | ||||||||
Item missing data (range %) | 1–2 | 3–4 | 2–4 | 3–4 | 2 | 2–4 | 2–4 | 1–2 |
Computable scale scores (%) | 98 | 97 | 98 | 97 | 98 | 98 | 96 | 99 |
Corrected item-total correlations | ||||||||
Mean | 0.76 | 0.82 | 0.78 | 0.87 | 0.89 | 0.83 | 0.78 | 0.82 |
Range | 0.67–0.81 | 0.70–0.87 | 0.64–0.87 | 0.82–0.91 | 0.84–0.93 | 0.79–0.89 | 0.68–0.84 | 0.70–0.90 |
Item-other scale correlations | ||||||||
Range | 0.37–0.72 | 0.40–0.75 | 0.43–0.72 | 0.42–0.75 | 0.39–0.52 | 0.42–0.73 | 0.39–0.82 | 0.38–0.69 |
Scaling successes (%) | 83 | 80 | 100 | 100 | 100 | 100 | 86 | 100 |
Targeting | ||||||||
Mean score | 57.6 | 53.8 | 42.9 | 37.1 | 33.3 | 37.9 | 29.7 | 49.2 |
Standard deviation | 25.6 | 27.9 | 27.6 | 31.5 | 31.5 | 26.9 | 24.9 | 29.5 |
Score range | 0–100 | 0–100 | 0–100 | 0–100 | 0–100 | 0–100 | 0–100 | 0–100 |
Floor/ceiling effect (%) | 1/6 | 2/7 | 7/0 | 17/4 | 27/7 | 7/4 | 13/1 | 5/4 |
Skewness | -0.23 | -0.15 | 0.11 | 0.44 | 0.66 | 0.51 | 0.82 | 0.02 |
Reliability (n = 377–385) | ||||||||
Cronbach's alpha | 0.92 | 0.93 | 0.94 | 0.97 | 0.96 | 0.96 | 0.95 | 0.96 |
TRT (ICC; n = 92–95) | 0.85 | 0.83 | 0.94 | 0.95 | 0.86 | 0.83 | 0.85 | 0.89 |