Stephen Hillis Stephen Hillis has been a Research Professor in the Department of Radiology since 2012. His educational background includes a PhD in statistics and an MFA in music, both from the University of Iowa. He is the author of more than 100 peer-reviewed publications and 4 book chapters.  Since 1999 his research has focused on developing statistical methods for analyzing radiologic diagnostic studies that involve human readers. He was introduced to this field in 1999 when he began working with Don Dorfman in the Dept. of Psychology at The University of Iowa.