Unbiased Online Active Learning in Data Streams Wei Chu ∗ Microsoft Redmond, WA, USA chu.wei@microsoft.com Martin Zinkevich Yahoo! Labs Sunnyvale, CA, USA maz@yahoo-inc.com Lihong Li Yahoo! Labs Sunnyvale, CA, USA lihong@yahoo-inc.com Achint Thomas Yahoo! Labs Sunnyvale, CA, USA aothomas@yahoo-inc.com Belle Tseng Yahoo! Labs Sunnyvale, CA, USA belle@yahoo-inc.com ABSTRACT Unlabeled samples can be