About the Authors Jeff Sauro is a six-sigma trained statistical analyst and founding principal of Measuring Usability LLC. For fifteen years he's been conducting usability and statistical analysis for companies such as PayPal, Walmart, Autodesk and Kelley Blue Book or working for companies such as Oracle, Intuit and General Electric. Jeff has published over fifteen peer-reviewed research articles and is on the editorial board of the Journal of Usability Studies. He is a regular presenter and instructor at the Computer Human Inter- action (CHI) and Usability Professionals Associations (UPA) conferences. Jeff received his Masters in Learning, Design and Technology from Stanford University with a concentration in statistical concepts. Prior to Stanford, he received his B.S. in Information Manage- ment & Technology and B.S. in Television, Radio and Film from Syracuse University. He lives with his wife and three children in Denver, CO. Dr. James R. (Jim) Lewis is a senior human factors engineer (at IBM since 1981) with a current focus on the design and evaluation of speech applications and is the author of Practical Speech User Interface Design. He is a Certified Human Factors Professional with a Ph.D. in Experimental Psychology (Psycholinguistics), an M.A. in Engineering Psychology, and an M.M. in Music Theory and Composition. Jim is an internationally recognized expert in usability testing and measurement, contributing (by invitation) the chapter on usability testing for the 3rd and 4th editions of the Hand- book of Human Factors and Ergonomics and presenting tutorials on usability testing and metrics at