Gwet's AC1
Gwet's AC1 is a chance-corrected agreement coefficient introduced by Kilem Gwet in 2008 as a robust alternative to Cohen's and Fleiss' kappa. It targets the kappa paradox — the unsettling result where coders agree on the vast majority of units yet kappa is near zero because one category dominates — by estimating chance agreement in a way that does not collapse when category prevalence is extreme.
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Sources
- Gwet, K. L. (2008). Computing inter-rater reliability and its variance in the presence of high agreement. British Journal of Mathematical and Statistical Psychology, 61(1), 29–48. DOI: 10.1348/000711006X126600 ↗
- Cohen, J. (1960). A coefficient of agreement for nominal scales. Educational and Psychological Measurement, 20(1), 37–46. DOI: 10.1177/001316446002000104 ↗
- Scott, W. A. (1955). Reliability of content analysis: The case of nominal scale coding. Public Opinion Quarterly, 19(3), 321–325. DOI: 10.1086/266577 ↗
How to cite this page
ScholarGate. (2026, June 22). Gwet's AC1 Agreement Coefficient. ScholarGate. https://scholargate.app/en/communication/gwet-ac1-reliability
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
- Fleiss' KappaStatistics↔ compare
- Intercoder ReliabilityCommunication↔ compare
- Krippendorff's AlphaCommunication↔ compare
- Scott's PiCommunication↔ compare