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.