Articles by Philip Kortum, PhD

Dr. Kortum is a faculty member in the Department of Psychology at Rice University in Houston, Texas. His primary interests are in the research and development of highly usable systems in the voting and mobile computing domains and in the characterization of measures of usability and usable systems.

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]

When Links Change: How Additions and Deletions of Single Navigation Links Affect User Performance

Abstract This study examined user performance for Web sites in which a critical navigation link may have changed over the course of two visits. These second visits occurred either immediately after the first visit, one week later, or three weeks later. A shortcut link to the information was either consistently present, consistently absent, or varied […] [Read More]

Determining What Individual SUS Scores Mean: Adding an Adjective Rating Scale

Abstract The System Usability Scale (SUS) is an inexpensive, yet effective tool for assessing the usability of a product, including Web sites, cell phones, interactive voice response systems, TV applications, and more. It provides an easy-to-understand score from 0 (negative) to 100 (positive). While a 100-point scale is intuitive in many respects and allows for […] [Read More]