Experiences in Remote Usability Evaluations  

Traditional usability testing occurs in a laboratory setting in which users are directly observed by test facilitators. However, the costs associated with accessing users for usability testing as well as the limited availability of many users make it necessary to consider new methods for gathering usability feedback for software products. Online, remote testing is a key to achieving a larger, more diverse pool of participants.

Cheatham, Deane and Velda Bartek. IBM (2004). Articles>Usability>Testing