Fig. 1: Two observers independently assess the presence or absence of a finding or outcome. Each observer determines that the finding is present in exactly 50% of the subjects. Their assessments agree in 75% of the cases. The yellow horizontal bar represents potential agreement (100%), and the turquoise bar represents actual agreement. The portion of each coloured bar that lies to the left of the dotted vertical line represents the agreement expected by chance (50%). The observed agreement above chance is half of the possible agreement above chance. The ratio of these 2 numbers is the kappa score.