Articles by Bernard Rummel

Mr. Rummel is trained in experimental psychology and has been working in the Usability and UI Design field for over 20 years. After nine years at the German Naval Medical Institute, he joined SAP in 2000, where he is currently responsible for usability testing methodology and participating in the national standardization body DIN.

Beyond Average: Weibull Analysis of Task Completion Times

Abstract Weibull analysis is an established method in technical reliability analysis for describing and analyzing the lifetime of technical parts. This paper describes the approach and demonstrates its application on task completion times from small-sample usability tests. Fitting a Weibull distribution model to observed data lets the analyst estimate task completion rates for any given […] [Read More]

Probability Plotting: A Tool for Analyzing Task Completion Times

Abstract Task completion time is a valuable metric for assessing or comparing the usability of a product. In online, unmoderated usability tests and other automated user behavior tracking methods, the large amount of time data that such tests yield must be carefully examined to exclude invalid data before further analysis can be meaningful. Other methodological […] [Read More]