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| Omega di McDonald per dati politomici× | Alpha di Cronbach ordinale× | |
|---|---|---|
| Campo | Psicometria | Psicometria |
| Famiglia | Latent structure | Latent structure |
| Anno di origine≠ | 1999 (omega); 2007 (polytomous extension) | 2007 |
| Ideatore≠ | Roderick P. McDonald (omega); extension for polytomous items by Zumbo, Gadermann & Zeisser | Zumbo, Gadermann, and Zeisser |
| Tipo≠ | Reliability coefficient | Internal consistency reliability 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. DOI ↗ | Zumbo, B. D., Gadermann, A. M., & Zeisser, C. (2007). Ordinal versions of coefficients alpha and theta for Likert rating scales. Journal of Modern Applied Statistical Methods, 6(1), 21–29. DOI ↗ |
| Alias | ordinal omega, omega for polytomous items, categorical omega, omega polychoric | alpha for ordinal data, polychoric alpha, ordinal reliability coefficient, alpha based on polychoric correlations |
| Correlati | 3 | 3 |
| Sintesi≠ | Polytomous McDonald's omega estimates the internal consistency reliability of a scale composed of ordinal (polytomous) items — such as Likert-type responses — by computing omega from a factor model fitted to the polychoric correlation matrix rather than the Pearson correlation matrix, yielding estimates that are unbiased by the discreteness of item responses. | Ordinal Cronbach's alpha is a reliability coefficient computed from polychoric or polyserial correlations rather than Pearson correlations, making it appropriate for Likert-type and other ordinal item response data. It corrects the systematic downward bias that standard Cronbach's alpha produces when items are treated as continuous but are actually ordinal. |
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