Ratings by observers are often used in speech pathology to measure complex speech dimensions; this seems reasonable since a speech “disorder” represents the product of an observer’s evaluation and a speaker’s performance. An index of the validity of these evaluations may be estimated by the amount of agreement among the observers. In this paper, the semi-interquartile range and the intraclass correlation are discussed as possible indices of agreement, and another index is suggested, based on the range of observer ratings. Under the assumption that the distribution of ratings is uniform when ratings are randomly assigned, that is, the observers show no agreement, tables were constructed to indicate the probability of any range for selected numbers of observers and rating scale categories. Some applications for this index concern the training of observers, estimating the number of observers needed, and the construction of master scales.
