Evaluation of consensus among experts: Kappa type indexes, models and properties

In many applications the importance of evaluating the consensus is growing. This is particularly important in many biomedical studies where the role of the experts is crucial. That is the case when the efficacy of treatments, the classification of patients, the quality of the biosphere in certain places or tests is studied. This paper is devoted to the development of a review of the Kappa index, indexes deduced or deducible from it as particular cases under certain models. Properties of them for different models are discussed. The models support parametric inferences or provide a statistical frame for analyzing the consensus in the classification among experts. Different examples are developed with illustrating purposes.