The test administrators adopted the cooperative evaluation [10] approach, which encourages users to think of themselves as collaborators with the designer to make the system better, rather than simply experimental subjects. The various techniques used for the initial experiments --- observation, think-aloud, transaction logs and interviews --- are qualitative methods. These are also known as ``ex post facto procedures'' since they do not identify an independent variable, and involve interpteting the findings after the fact rather than setting out hypotheses before conducting the tests.