Scott's pi Expert Working Group Agreement: 2022-10-19 vote 6-0 by Joanne Dehnbostel, Muhammad Afzal, Jesus Lopez-Alcalde, Mario Tristan, Eric Harvey, Harold Lehmann A Kappa statistic where the expected agreement between two raters is expressed in terms of the square of arithmetic means of marginal proportions of each assessment category. Scott's pi is a kappa statistic for two raters that assumes the likelihood of each category for assignment is based on the same distribution of rater responses, leading to the use of squared arithmetic means of the marginal proportion of each assessment category as its estimate of "chance agreement." Pr(expected) is calculated using squared "joint proportions" which are squared arithmetic means of the marginal proportions of each assessment category, in contrast to Cohen's Kappa which uses squared geometric means. Scott's pi = ( p[a] - p[e] ) / ( 1 - p[e] ) where p[a] is the observed percent agreement and p[e] is the expected chance agreement expressed as the squared joint proportions of the marginal sums. Brian S. Alper, Harold Lehmann, Joanne Dehnbostel, Muhammad Afzal, Kenneth Wilkins kappa ready for release