Understanding and Computing Cohen’s Kappa: A Tutorial.
Cohen’s Kappa (Cohen, 1960) is an index of interrater reliability that is commonly used to measure the level of agreement between two sets of dichotomous ratings or scores. This tutorial explains the underlying logic of Kappa and shows why it is superior to simple percentage of agreement as a measure of interrater reliability. Examples demonstrate how to calculate Kappa both by hand and with SPSS.
James M. Wood. "Understanding and Computing Cohen’s Kappa: A Tutorial." WebPsychEmpiricist. Web Journal at http://wpe.info/ (2007).