# Fleiss Kappa

Fleiss' Kappa stastistic is a measure of the inter-rater agreement. This statistic is an extension of Cohen's Kappa to situations when there are more than two raters. Fleiss' Kappa is used when the categorical variable being measured is nominal and it takes into account the fact that even if two observers use completely different criteria to classify subjects we would expect the observers to agree merely by chance. Thus Fleiss' Kappa statistic is a measure of the extent to which the raters agree beyond what we expect by chance alone.
-- ErinEsp - 25 Jul 2010