<unk>  coefficient is a statistical measure of inter-rater reliability.  It is generally thought to be a more robust measure than simple percent agreement calculation since κ takes into account the agreement occurring by chance.<unk>  measures the agreement between two raters who each classify N items into C mutually exclusive categories.
The equation for κ is:
where Pr(a) is the relative observed agreement among raters, and Pr(e) is the probability that agreement is due to chance.  If the raters are in complete agreement then κ = 1.  If there is no agreement among the raters (other than what would be expected by chance) then κ ≤ 0.
The seminal paper introducing<unk>  as a new technique was published by Jacob<unk>  in the journal Educational and Psychological Measurement in 1960.
Note that<unk>  measures agreement between two raters only.  For a similar measure of agreement (Fleiss'<unk>  used when there are more than two raters, see Fleiss (1981).
Cohen's kappa
Brown-Forsythe test
Kendall tau rank correlation coefficient
Shapiro-Wilk test
Ancillary statistic
Likelihood-ratio test
Analysis of rhythmic variance
Chi-square test