Intraclass Correlation (ICC1, ICC2)
HR & WorkReliability: statistical estimator4 sample items
About this scale
Two complementary ICC indices for justifying group-level aggregation. ICC(1) is the proportion of variance attributable to group membership; ICC(2) is the reliability of group means. Both reported alongside rwg.
Sample item(s)
“Run one-way ANOVA on the variable”
“ICC(1) = (MSb - MSw) / [MSb + (k-1) MSw]”
“ICC(2) = (MSb - MSw) / MSb”
“ICC(1) ≥ 0.05 + ICC(2) ≥ 0.70 supports aggregation”
Reliability
Reported internal consistency: statistical estimator. As a rule of thumb, Cronbach’s α ≥ .70 is considered acceptable, ≥ .80 good, and ≥ .90 excellent for established measures.
Notes
Standard multilevel aggregation methods.
Source & citation
Bliese, P. D. (2000): Within-group agreement, non-independence, and reliability: Implications for data aggregation and analysis. In K. J. Klein & S. W. J. Kozlowski (Eds.), Multilevel theory, research, and methods in organizations (pp. 349–381). Jossey-Bass.
Source. Scale details are summarised from the publication cited above. Always consult the original source for the full item set, scoring, and permission to use.
Use it in your research
Need to check the reliability or psychometrics of this scale in your own data? Use the free DrAIStudio research tools:
Cronbach’s alpha calculator
All statistical calculators
Search the full Scale Atlas
Academic writing humanizer