Kendall's coefficient of concordance (KCC)

Indicates the degree of association of ordinal assessments made by multiple appraisers when evaluating the same samples. Kendall's coefficient is commonly used in attribute agreement analysis (attribute gage R&R).

For example, chicken wings are rated on a 1-10 scale. The consequences of misclassifying a suicide hot wing (10) as medium (5) are more serious than misclassifying it as intensely hot (8).

Kendall's values range from 0 to +1. The higher the value of Kendall's, the stronger the association. Generally Kendall's coefficients of 0.9 or above are considered very good. A high or significant Kendall's coefficient means that the appraisers are applying essentially the same standard when evaluating the samples.

Kendall's correlation coefficient

If you provide a known rating for each sample, Minitab also calculates Kendall's correlation coefficients. The correlation coefficients are given for each appraiser to indicate the agreement of each appraiser with the known standard; and an overall coefficient to represent all appraisers with the standards. The correlation coefficient helps you determine whether an appraiser is consistent but inaccurate.