Omega (ω)

A model-based estimate of a scale's reliability, often preferred over Cronbach's alpha because it makes more realistic assumptions.

McDonald's omega (ω) is a measure of internal-consistency reliability estimated from a factor-analytic model of the items. Like Cronbach's alpha, it summarizes how consistently a set of items measures a single construct, on a 0–1 scale.

Omega is increasingly recommended over alpha because alpha assumes every item contributes equally (equal factor loadings, or "tau-equivalence") — an assumption that is rarely true. Omega instead uses the items' actual estimated loadings, so it is usually a more accurate reliability estimate. Reporting omega alongside or in place of alpha has become common in contemporary validation papers.

Cronbach's alpha (α) — A statistical measure of how internally consistent the items on a scale are; ≥ 0.7 is typically acceptable.
Internal consistency — The degree to which items on a scale correlate with one another, suggesting they measure the same construct.
Reliability — The consistency of an assessment's results across repeated administrations and across items.
Factor analysis — A family of statistical methods for identifying the underlying latent factors that explain correlations among observed items.

Omega (ω)

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