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	Analisi di Affidabilità Ordinale	Omega gerarchico di McDonald (ωh)
Campo	Psicometria	Psicometria
Famiglia	Latent structure	Latent structure
Anno di origine	2007	1999
Ideatore	Bruno D. Zumbo and colleagues	Roderick P. McDonald
Tipo	Internal consistency reliability estimation	Reliability / composite score validity coefficient
Fonte seminale	Zumbo, B. D., Gadermann, A. M. & Zeisser, C. (2007). Ordinal versions of coefficients alpha and theta as measures of internal consistency for Likert rating scales. Journal of Modern Applied Statistical Methods, 6(1), 21–29.	Reise, S. P., Scheines, R., Widaman, K. F. & Haviland, M. G. (2013). Multidimensionality and structural coefficient bias in structural equation modeling: A bifactor perspective. Educational and Psychological Measurement, 73(1), 5–26.
Alias	ordinal alpha, polychoric reliability, reliability for ordinal scales, ORA	omega hierarchical, omega-h, bifactor omega, composite score validity coefficient
Correlati	5	5
Sintesi	Ordinal reliability analysis estimates the internal consistency of scales whose items are measured on ordered-category (Likert-type) response formats. By basing computations on polychoric correlations rather than Pearson correlations, it corrects for the attenuation that standard Cronbach's alpha produces when responses are discrete and non-normal.	McDonald's hierarchical omega (ωh) is a coefficient derived from a bifactor confirmatory factor model that quantifies what proportion of total-score variance is attributable to a single general factor rather than to group-specific factors or item-level error. Introduced by Roderick P. McDonald (1999) and elaborated for bifactor applications by Reise and colleagues (2013) and Rodriguez and colleagues (2016), it is the primary index used in psychometrics to evaluate whether a composite total score is a defensible summary of a multidimensional scale.