Articles by Philip Kortum, PhD

Dr. Kortum is an Associate Professor in the Department of Psychological Sciences at Rice University in Houston, Texas. His research is focused on the development and refinement of measures of usability and trust, and on creating highly usable systems in the global health, mobile, and voting system domains.

Validity of Three Discount Methods for Measuring Perceived Usability

Abstract Within the domain of subjective usability assessment, several potential discount methods exist. However, there is little or no prior research investigating how these methods compare in their impact on subjective usability ratings. This study compared four methods of collecting subjective usability data with the System Usability Scale (SUS). Users were asked to use and […] [Read More]

SUSapp: A Free Mobile Application That Makes the System Usability Scale (SUS) Easier to Administer

Abstract The System Usability Scale (SUS), created by Brooke (1996), is a widely used measure to assess subjective usability. However, few digital tools have been created to help collect the required data and compute SUS scores, which rely upon a formula that is complex. The aim of the project was to develop an open-source iOS […] [Read More]

Has Human Factors and Usability Lost Its Mojo?

Introduction The human factors and usability community has contributed greatly to the safety, usability, and general acceptance of systems over the last 70 years. The tireless work of countless researchers and practitioners has had a significant positive impact on society. Although there are untold numbers of success stories where human factors and usability professionals have […] [Read More]

How Hard Can It Be to Place a Ballot Into a Ballot Box? Usability of Ballot Boxes in Tamper Resistant Voting Systems

Abstract End-to-end verifiable voting methods are an emerging type of voting system, and a number of new designs are being actively developed. Many of these systems try to mirror current paper voting methods and use a paper ballot that can be scanned and then placed into a ballot box. Previous research has shown that having […] [Read More]

How Low Can You Go? Is the System Usability Scale Range Restricted?

Abstract Previous research suggests that the System Usability Scale (SUS) might not be generating usability scores that span the entire measurement range from 0 to 100, particularly at the lower end of the scale. Most published literature has reported study mean scores that are typically above 40. The use of only a subset of the […] [Read More]