Sample-size calculations for Cohen's kappa

In recent years, researchers in the psychosocial and biomedical sciences have become increasingly aware of the importance of sample-size calculations in the design of research projects. Such considerations are, however, rarely applied for studies involving agreement of raters. Published results on this topic are limited and generally provide rather complex formulas. In addition, they generally make the assumption that the raters have the same set of frequencies for the possible ratings. In this article I show that for the case of 2 raters and 2 possible ratings the assumptions of equal frequencies can be dropped. Tables that allow for almost immediate sample-size determination for a variety of common study designs are given.