Summary of Rasch analysis
| Rasch statistics | BHQ total score |
| Number of items | 10 |
| Chi-squared fit statistic | 28.16 |
| Degrees of freedom | 20 |
| p-value | 0.11 |
| Item fit residual (mean±sd) | 0.01±1.11 |
| Person fit residual (mean±sd) | −0.25±1.11 |
| PSI | 0.85 |
| Cronbach's α | 0.85 |
BHQ: Bronchiectasis Health Questionnaire; PSI: Person Separation Index. The Chi-squared statistic assesses item–trait interaction; nonsignificance indicates a good fit to the Rasch model (p>0.05). The mean person and item fit residuals are item–person interaction statistics that are z-transformed; a good fit to the Rasch model is when they approximate to a mean±sd of 0±1. The PSI assesses how well BHQ discriminates subjects with differing levels of health status. Cronbach's α coefficient is a measure of internal reliability. A PSI and Cronbach's α coefficient ≥0.7 is considered acceptable.