Interitem and item–total correlations and effects of removing items on internal consistency
| Interitem correlation matrix | Item–total correlation | Cronbach's α if item deleted | |||
|---|---|---|---|---|---|
| Question 1 | Question 2 | Question 3 | |||
| All questionnaires (n=4470) | |||||
| Question 1 | – | 0.92 | 0.94 | ||
| Question 2 | 0.87 | – | 0.90 | 0.94 | |
| Question 3 | 0.89 | 0.88 | – | 0.92 | 0.94 |
| Question 4 | 0.85 | 0.80 | 0.84 | 0.87 | 0.95 |
| Non-injury cases (n=3384) | |||||
| Question 1 | – | 0.94 | 0.95 | ||
| Question 2 | 0.91 | – | 0.91 | 0.96 | |
| Question 3 | 0.90 | 0.91 | – | 0.94 | 0.95 |
| Question 4 | 0.87 | 0.82 | 0.88 | 0.88 | 0.96 |