Table 5 Rationale for possible items for deletion
Item | Rationale | Decision | ||
|---|---|---|---|---|
Inter-item correlation | Item properties | IRT modelling | ||
3. Reading on Tablet Device | Potential redundancy with item 2 (0.973) and 4 (0.983) Item 2. Reading on a smartphone Item 4. Reading on a laptop or desktop | Most participants noted doing this activity between Baseline and Month 3 | Potential local dependency with Item 2 and 4 | Remove item |
8. Engaging in Hobbies | Inter-item correlations were less than 0.9 | High percentage of participants endorsing the N/A response option (20.0-25.1%) between Baseline and Month 3 | No evidence of local dependency | Retain– despite 20% of participants endorsing N/A option, the item assesses a slightly different concept to other items |
14. Reading for Long Period of Time | Inter item correlations were less than 0.9 | Most participants noted doing this activity between Baseline and Month 3 | Potential local dependency with Item 15 (Adjusting vision from long distance to short distance) | Retain– despite potential local dependency with item 15, the items assess slightly different concepts |