The Return on Usability Testing
http://www.gotomedia.com/gotoreport/may2005/news_0505_roi.html

Subramanian, Subha
GotoMedia
2005

Abstract:

Usability testing is the qualitative measurement of user experience with a product or service, such as a website. Usability testing is for anyone who wants to make their website, software, device, etc. easier to use. Whether you employ thousands of people such as Microsoft or fall into the small business category, usability testing can play a significant role in giving you direct feedback from your customers.