In 1998, usability expert Rolf Molich (co-inventor with Jakob Nielsen of the heuristic evaluation method) gave nine teams three weeks to evaluate the webmail application www.hotmail.com. The experiment was part of his series of Comparative Usability Evaluations (CUEs), through which he began to identify a set of standards and best practices for usability tests. In each segment of the series, Molich asked several usability teams to evaluate a single design using the method of their choice.
From the documented results of the second test, called CUE-2, a surprising trend appeared. Contrary to claims that usability professionals operate scientifically to identify problems in an interface, usability evaluations are at best less than scientific.