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	Coefficiente di affidabilità Omega (ω) di McDonald	Modello di Rasch
Campo	Psicometria	Psicometria
Famiglia	Latent structure	Latent structure
Anno di origine	1999	1960
Ideatore	Roderick P. McDonald	Georg Rasch
Tipo	Reliability coefficient / latent variable model	Item Response Theory / Latent trait model
Fonte seminale	McDonald, R. P. (1999). Test Theory: A Unified Treatment. Lawrence Erlbaum Associates. ISBN: 978-0805830750	Rasch, G. (1960). Probabilistic Models for Some Intelligence and Attainment Tests. Danish Institute for Educational Research, Copenhagen.
Alias	omega reliability, ω coefficient, omega total, omega hierarchical	1PL IRT, one-parameter logistic model, Rasch Modeli — 1PL IRT, 1PL model
Correlati	6	6
Sintesi	McDonald's omega is a factor-analysis-based reliability coefficient introduced by Roderick P. McDonald (1999) that quantifies the internal consistency of a composite score without requiring the restrictive assumption that all items contribute equally to the latent factor. It yields two complementary indices: ω_total, which captures overall reliability of the sum score, and ω_hierarchical (ωh), which reports how much of the composite's variance is explained specifically by a single general factor.	The Rasch model, introduced by Georg Rasch in 1960, is the simplest member of the Item Response Theory (IRT) family. It assigns a single difficulty parameter to each test item and places both item difficulties and person abilities on the same logit scale, enabling direct, sample-independent comparison of items and persons.