%0 Journal Article %T When does Active Learning Work? %A Lewis Evans %A Niall M. Adams %A Christoforos Anagnostopoulos %J Computer Science %D 2014 %I arXiv %X Active Learning (AL) methods seek to improve classifier performance when labels are expensive or scarce. We consider two central questions: Where does AL work? How much does it help? To address these questions, a comprehensive experimental simulation study of Active Learning is presented. We consider a variety of tasks, classifiers and other AL factors, to present a broad exploration of AL performance in various settings. A precise way to quantify performance is needed in order to know when AL works. Thus we also present a detailed methodology for tackling the complexities of assessing AL performance in the context of this experimental study. %U http://arxiv.org/abs/1408.1319v1