Table 5 Scaling assumptions (classical test theory [CTT]).
Item | N | Scaling assumptions | ||||
|---|---|---|---|---|---|---|
Possible range (mid-point) | Actual score range | Mean score | Variance | CITC | ||
Behavioral impact | ||||||
TD09 use more than intended | 2434 | 1–5 (3) | 1–5 | 2.8 | 1.3 | 0.64 |
TD11 use in situations not supposed to | 2433 | 1–5 (3) | 1–5 | 2.2 | 1.5 | 0.72 |
TD16 sneak off to use | 2434 | 1–5 (3) | 1–5 | 2.1 | 1.5 | 0.76 |
TD17 avoid activity can’t use | 2434 | 1–5 (3) | 1–5 | 1.9 | 1.4 | 0.79 |
TD18 stop what doing to use | 2434 | 1–5 (3) | 1–5 | 2.4 | 1.6 | 0.77 |
Signs and symptoms | ||||||
TD03 function normally | 2434 | 1–5 (3) | 1–5 | 3.0 | 1.7 | 0.76 |
TD06 difficult to quit | 2434 | 1–5 (3) | 1–5 | 3.4 | 1.9 | 0.75 |
TD08 strong desire | 2434 | 1–5 (3) | 1–5 | 3.4 | 1.1 | 0.80 |
TD10 had to have one | 2434 | 1–5 (3) | 1–5 | 3.0 | 1.4 | 0.82 |
TD13 urge hard to control | 2434 | 1–5 (3) | 1–5 | 2.7 | 1.6 | 0.78 |
Extent of use | ||||||
TD01 after waking up | 2434 | 1–6 (3.5) | 1–6 | 3.5 | 2.7 | 0.71 |
TD02 before sleep | 2434 | 1–6 (3.5) | 1–6 | 3.5 | 2.3 | 0.71 |
