The Impact of Agile on User-Centered Design
http://www.ingentaconnect.com/content/stc/tc/2009/00000056/00000003/art00004
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  peer-reviewed

Dayton, David and Carol S. Barnum
Technical Communication Online
2009

Abstract:

Discusses the impact of an agile software development process on usability testing. Reports opinions about usability testing within a company before and after a change to agile. Presents strategies to incorporate usability testing into agile product development.