Intraclass Correlation ICC 2 1 Calculator
Calculate two-way random, absolute-agreement, single-measure ICC(2,1) from a complete rectangular ratings design.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Form two-way ANOVA mean squares for subjects, raters and residuals, then use the absolute-agreement single-measure denominator.
ICC(2,1)=(MSR−MSE)/(MSR+(k−1)MSE+k(MSC−MSE)/n)
Worked example
Four subjects with identical paired ratings (1,1),(2,2),(3,3),(4,4) give ICC(2,1)=1. A systematic rater offset reduces absolute agreement.
Assumptions and input details
Complete fully crossed subject-by-rater design only; enter rows as consecutive whitespace/comma-separated values. Raters are modeled as random and the result concerns one measurement, not an average. Negative estimates are retained; no confidence interval or universal interpretation threshold.
References: Koo and Li: ICC form selection and formula
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
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The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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