Expected correspondence = [(A+B)*(A+C))+[C+D]*(B+D))/(A+B+C+D) Taylor, D. R. A useful method for calculating Harris and Lahey`s weighted compliance formula. The Behavioural Therapist 1980,3, 3. Kappa is an index that takes into account the observed concordance with a basic agreement. However, researchers should carefully consider whether Kappa`s basic agreement is relevant to each research question. Kappas Baseline is often described as the agreement by chance, which is only partially correct. The Basic Kappa Agreement is the agreement that would be expected due to random allocation, given the quantities indicated by the marginal amounts of the square contingency table. Therefore, Kappa = 0, if the observed allocation is apparently random, regardless of the quantitative opinion limited by marginal amounts. . . .