Intraclass Correlation Coefficient

A reliability statistic that quantifies the proportion of total observed variance in continuous measurements attributable to between‑subject (or between‑target) variation within a specified measurement model; its numeric value depends on the chosen ICC form (e.g., one‑way random, two‑way mixed) and whether 'consistency' or 'absolute agreement' is defined.

A statistical index that quantifies the proportion of total variance in continuous or ordinal ratings attributable to differences between target units (e.g., subjects, items, groups) rather than to measurement error or rater variability, conditional on a specified model of effects.