Two raters can agree 90% of the time and still score a kappa of zero.
AgreeStat Analytics is Dr. Gwet's research and software home for measuring how well raters, coders, and diagnostic instruments actually agree — covering Cohen's Kappa, Gwet's AC1/AC2, Krippendorff's alpha, and intraclass correlation.
See the paradox for yourself
Edit the 2×2 table below. Watch raw agreement stay high while Cohen's Kappa collapses — and Gwet's AC1 stays honest.
| B: Yes | B: No | |
|---|---|---|
| A: Yes | ||
| A: No |
With the default counts, agreement runs high even though most subjects fall in one category. That's exactly the condition under which Kappa is known to misbehave — the puzzle Dr. Gwet's research addresses directly.
A working repository, not a brochure
Everything on this site exists to help you compute, defend, and publish inter-rater reliability results correctly.
Free articles
Dr. Gwet's published and unpublished papers on chance-corrected agreement coefficients, made freely available for researchers and reviewers.
Browse the papers →Computer programs
Download reliability-coefficient routines in R and SAS, built to reproduce the formulas exactly as documented in the Handbook.
Get the code →Book excerpts
Read excerpts from the current and forthcoming editions of the Handbook of Inter-Rater Reliability before you buy.
Read excerpts →Statistical analysis your committee can open in Excel
Compute chance-corrected agreement coefficients and intraclass correlation coefficients without leaving a spreadsheet your co-authors already trust.
Walkthrough of AgreeStat360 for Excel/Windows. Prefer a bigger screen? Watch on YouTube ↗
CAC statistics include Cohen's Kappa, Gwet's AC1/AC2, and Krippendorff's alpha. ICC statistics cover several coefficients built on different ANOVA models.
Handbook of Inter-Rater Reliability, 5th Edition
The reference text behind most of the methods on this site, now split by rating type — Volume 1 for categorical ratings, Volume 2 for quantitative ratings — so you only need the volume that matches your data.
No install required
Two free-to-try tools for teams who'd rather work from a browser tab than a spreadsheet.
AgreeStat360 / Cloud-Based
Point-and-click inter-rater reliability analysis, right in your browser. Register for a trial at agreestat360.com — any paid license key also works with AgreeStat360 for Excel/Windows.
AgreeTest / Cloud-Based
Test whether the difference between two agreement coefficients is statistically significant — entirely from your browser, no spreadsheet setup needed.
