Studies comparing performance of Usability Evaluation Methods (UEMs) led to three standard metrics, namely, validity, thoroughness, and effectiveness, calculated from lab-based usability test results. The effectiveness metric, E = T x V, was proposed as the 'figure of merit' that would give a balanced account of validity and thoroughness. This paper provides an analysis of the formula to caution future researchers and usability practitioners against its use, proposes an alternative formula, and discusses the limitations of the common baseline approach to UEM comparison.
Lecture notes in computer science: proceedings of 12th IFIP TC 13 International Conference on Human-Computer Interaction (INTERACT '09), Stockholm, Sweden, 26-28 August 2009, Vol. 5726, part I, pp. 235-238