Measuring ineffectiveness

An evaluation methodology that targets ineffective topics is needed to support research on obtaining more consistent retrieval across topics. Using average values of traditional evaluation measures is not an appropriate methodology be-cause it emphasizes effective topics: poorly performing top-ics ’ scores are by definition small, and they are therefore difficult to distinguish from the noise inherent in retrieval evaluation. We examine two new measures that empha-size a system’s worst topics. While these measures focus on different aspects of retrieval behavior than traditional mea-sures, the measures are less stable than traditional measures and the margin of error associated with the new measures is large relative to the observed differences in scores.