He received his bachelors degrees in Mathematics and Computer Science from Cornell University, and doctoral degree from MIT. He was a postdoc at UC Berkeley EECS before joining UPenn, where he is a co-director of the Penn Research in Machine Learning (PRiML) center. His research is in machine learning, with an emphasis on statistics and computation. Alexander is a recipient of the NSF CAREER award, IBM Research Best Paper award, Machine Learning Journal award, and COLT Best Paper Award.