Purpose: Differential Item Functioning (DIF), an item malfunctioning, causes Differential Test Functioning (DTF), thus biasing questionnaire measures. The current study evaluates the relationship between DIF and DTF for the Barthel Index and the Functional Independence Measure, likely the most used disability measures. The aim is to understand under which conditions DIF can be ignored as its DTF is negligible. Methods: A simulation study was run. Disability measures were obtained for the Barthel Index and FIM motor domain using Rasch analysis with previously published item calibrations. Several DIF scenarios have been assessed. DTF was tolerable if ≤0.50 logits. Results: Simulations showed that the larger the DIF, the larger the DTF and that, keeping the overall DIF constant, the total number of items with DIF does not affect DTF. DIF of the items with the lowest or highest calibrations is the most dangerous. The DIF of central items should be so massive to matter in DTF terms that it is unlikely to happen in practice. The FIM robustness to DIF is better than that of the Barthel Index. Conclusions: The FIM and the Barthel Index show remarkable robustness to DIF. Thanks to this feature, sample invariant, generalisable disability measures are available.

Generalisability of the Barthel Index and the Functional Independence Measure: robustness of disability measures to Differential Item Functioning / A. Caronni, S. Scarano. - In: DISABILITY AND REHABILITATION. - ISSN 0963-8288. - (2024 Sep 02), pp. 1-12. [Epub ahead of print] [10.1080/09638288.2024.2391554]

Generalisability of the Barthel Index and the Functional Independence Measure: robustness of disability measures to Differential Item Functioning

A. Caronni
Primo
;
S. Scarano
Ultimo
2024

Abstract

Purpose: Differential Item Functioning (DIF), an item malfunctioning, causes Differential Test Functioning (DTF), thus biasing questionnaire measures. The current study evaluates the relationship between DIF and DTF for the Barthel Index and the Functional Independence Measure, likely the most used disability measures. The aim is to understand under which conditions DIF can be ignored as its DTF is negligible. Methods: A simulation study was run. Disability measures were obtained for the Barthel Index and FIM motor domain using Rasch analysis with previously published item calibrations. Several DIF scenarios have been assessed. DTF was tolerable if ≤0.50 logits. Results: Simulations showed that the larger the DIF, the larger the DTF and that, keeping the overall DIF constant, the total number of items with DIF does not affect DTF. DIF of the items with the lowest or highest calibrations is the most dangerous. The DIF of central items should be so massive to matter in DTF terms that it is unlikely to happen in practice. The FIM robustness to DIF is better than that of the Barthel Index. Conclusions: The FIM and the Barthel Index show remarkable robustness to DIF. Thanks to this feature, sample invariant, generalisable disability measures are available.
Disability measurement; Rasch analysis; item bias; psychometrics; rehabilitation
Settore MEDS-19/B - Medicina fisica e riabilitativa
2-set-2024
Article (author)
File in questo prodotto:
File Dimensione Formato  
Generalisability of the Barthel Index and the Functional Independence Measure - robustness of disability measures to Differential Item Functioning.pdf

accesso aperto

Descrizione: Article
Tipologia: Publisher's version/PDF
Dimensione 2.68 MB
Formato Adobe PDF
2.68 MB Adobe PDF Visualizza/Apri
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/1097512
Citazioni
  • ???jsp.display-item.citation.pmc??? 0
  • Scopus 0
  • ???jsp.display-item.citation.isi??? 0
social impact