Sample size requirements for interval estimation of the intraclass kappa statistic

Sample size requirements that achieve a prespecified expected width or lower limit for a confidence interval about the intraclass kappa statistic are supplied for the case of two raters and a dichotomous outcome measure. These results should be useful in the planning stages of an interobserver agreement study in which the focus is on estimation rather than hypothesis-testing. In order to quantify the loss of precision obtained when choosing a dichotomous trait for this purpose, corresponding results are also provided for the case of a continuous outcome measure.