A Single-Item Measure of Website Usability: Comments on Christophersen and Konradt (2011)
Christophersen and Konradt show that a single-item measure of usability can retain most of the information garnered in multi-item scale. While there is some loss of information and reliability, the authors show that when a single item is needed, it can be reliable, sensitive (discriminate between good and bad usability) and valid (correlates with other known measures of usability).
usability testing