Agreement, the F-measure, and reliability in information retrieval

Information retrieval studies that involve searching the Internet or marking phrases usually lack a well-defined number of negative cases. This prevents the use of traditional interrater reliability metrics like the K statistic to assess the quality of expert-generated gold standards. Such studies often quantify system performance as precision, recall, and F-measure, or as agreement. It can be shown that the average F-measure among pairs of experts is numerically identical to the average positive specific agreement among experts and that K approaches these measures as the number of negative cases grows large. Positive specific agreement-or the equivalent F-measure may be an appropriate way to quantify interrater reliability and therefore to assess the reliability of a gold standard in these studies.