AbstractThe retrieval effectiveness of large document collections is normally assessed by using small subsections of the file for test purposes, and extrapolating the data upward to represent the results for the full collection. The accuracy of such an extrapolation unhappily depends on the “generality” of the respective collections.In the present study the role of the generality effect in retrieval system evaluation is assessed, and evaluation results are given for the comparison of several document collections of distinct size and generality in the areas of documentation and aerodynam