R-3 Repository :: Browsing by Author "Kortum, Philip T"

Browsing by Author "Kortum, Philip T"

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Checking Your Answers: An Investigation of Alternative Review Screen Design for Electronic Voting Systems
(2015-04-21) Holmes, Danae V; Kortum, Philip T; Byrne, Michael D; Lane, David M; Wallach, Dan S
Verifying a ballot for correctness in an election is a critical task considering the large, negative repercussions of an incorrect ballot. Studies have shown weaknesses in the ballot review process in electronic voting systems, allowing up to 30% of the ballot to be changed without being noticed by 68% of voters (Everett, 2007). There is also a noted lack of research on the effect of navigation style on electronic voting system usability and review screen performance. In response to these issues, this study evaluated the usability and viability of alternative ballot verification and navigation methods in an electronic voting medium, specifically direct recording electronic (DRE) voting systems. Currently, most DRE’s employ an end-of-ballot review where all selections are confirmed at once at the end of the ballot, which has been proven to be ineffective. Several studies (Holmes and Kortum, 2013; Selker 2007) have also indicated that in-line confirmation, confirming each selection immediately after making it, and a combination of the two confirmation methods (Ghandi et al., 2005; Cohen et al., 1996) may prove to be a suitable alternatives. The current study tested these methods of verification in terms of performance and usability to determine whether they are viable methods of verification as well as to provide a benchmark for review screen performance in a DRE. The method of navigation through the ballot, the ability to move backwards through the ballot or not after selecting a candidate, was also tested for its impact on usability and performance. The verification methods were evaluated on three metrics of usability as defined by ISO 9241 part 11; efficiency (time to complete a ballot), effectiveness (errors), and satisfaction (subjective usability). Participants cast their ballot in a mock national election using a custom DRE interface. Results indicate that in-line and dual confirmation methods prove to be viable alternatives for DRE review screens. In-line and dual confirmation perform similarly to end-of-ballot confirmation in terms of effectiveness, but differed in other usability and performance aspects, though not necessarily in a negative way. The most efficient method is end-of-ballot review, and dual confirmation produced the longest time spent on the review screen. End-of-ballot confirmation produced the highest satisfaction ratings, though survey results indicated that dual confirmation may be the most appropriate method in terms of voting. Based on the results from this study, further studies should be conducted to determine which confirmation method performs best as an error prevention tool.
Clinical Evaluation of an Upper Limb Exoskeleton for Rehabilitation After Incomplete Spinal Cord Injury
(2015-04-21) Fitle, Kyle D; O'Malley, Marcia K.; Dick, Andrew J; Kortum, Philip T
In recent years robotic rehabilitation has emerged as an effective rehabilitation tool for motor impairment caused by multiple types of injuries and ailments. Incomplete spinal cord injury (SCI) is one of the injury types which is a prime candidate for robotic rehabilitation, but this field is relatively young and unexplored. The MAHI Exo II is a five degree-of-freedom (DOF) robotic exoskeleton which was designed for rehabilitation of the upper-limb following SCI or stroke. Upper-limb impairment is one of the factors which SCI patients rate as most significant in their post-injury decrease in quality of life. Therefore, the MAHI Exo II has the potential to make strides in improving the quality of life of patients in novel ways. This thesis presents research which has been done towards this aim. The first section presents a study on incomplete SCI rehabilitation with the MAHI Exo II. This study used the robotic system to provide resistance therapy for elbow flexion/extensioin, forearm pronation/supination, wrist flexion/extension, and wrist radial/ulnar deviation. The robot was also used to record position data in a backdriving-evaluation mode in order to analyze the change in subject movement quality over the course of therapy using several robotic quality of movement metrics. Subject improvement was also measured by standard clinical impairment measures used for SCI. Ten subjects enrolled in the study and eight finished the entire protocol. The results of this study spurred further research into more effective control and treatment strategies for the MAHI Exo II. In the second portion of this thesis, I present details on the Assist-as-Needed rehabilitation study. This experiment sought to apply assistive therapy with the MAHI Exo II using a novel adaptive control strategy and compare it to a non-adaptive controller in a parallel controlled study. This type of comparison has not been done before for robotic rehabilitation. The assistive nature of the controller allowed a wider inclusion criteria for incomplete SCI. The same joints were trained in this study and most of the same clinical and robotic measures were used to evaluate motor ability improvement. One of the secondary features of the study design is the sequential group assignment with co-variates minimization. The study is currently in progress at the time of this writing, but some preliminary results are presented in this section.
Factors Influencing Speed-Accuracy Tradeoffs
(2014-11-13) Zemla, Jeffrey Clark; Byrne, Michael D; Kortum, Philip T; Schnur, Tatiana; Batsell, Richard R
Many simple decisions allow us to trade o between speed and accuracy. When time is critical, decisions can be made quickly but accuracy su ers. Conversely, one may spend more time making a decision which often results in more accurate decisions. Speed-accuracy tradeo s have been studied in a number of domains including motor control (Fitts, 1954), perception (Usher & McClelland, 2001), and higher order reasoning (Kahneman & Frederick, 2002). Recent research has examined a set of normative models for how one should trade o speed and accuracy (Bogacz, Brown, Moehlis, Holmes, & Cohen, 2006); that is, how long someone should spend deliberating prior to action in order to maximize some reward. However, empirical work has shown haphazard adherence to these normative models (e.g., Zacksenhouse, Bogacz, & Holmes, 2010). While some subjects behave optimally, many do not. In two experiments, several factors that a ect speed-accuracy tradeo s in a perceptual decision-making task are investigated. In one experiment, it was found that feedback and shorter blocks not only improved participants’ task ability, but also resulted in more optimal speed-accuracy tradeo s. In a second experiment, manipulating trial di culty and subjects’ awareness of di culty level a ected task performance. However, despite predictions from a normative theory, participants did not engage in an optimal speed-accuracy tradeo policy.
Multi-Cultural Usability Assessment with System Usability Scale
(2019-07-30) Gao, Mei; Kortum, Philip T
The System Usability Scale (SUS) is a non-proprietary and technology-agnostic instrument that measures the subjective usability of products and systems. Besides its popularity in the English Human Factors community, the SUS has also been translated to other languages such as Mandarin (Sheu, Fu, & Shih, 2017) and Polish (Borkowska & Jach, 2017). Although past research has demonstrated the reliability and validity of the SUS in some languages, methodology of validating translation was inconsistent between languages. This project aims to address this issue by translating and validating the SUS in multiple languages systematically. Native speakers of Arabic, Chinese, French, German, Hindi, and Spanish were recruited on Prolific.ac to evaluate five everyday products on the translated SUS. Evidence of scale reliability and validity was found in Chinese, French, German and Spanish SUS, with Cronbach’s alpha > 0.8 and significant correlations between SUS and an adjective rating scale (r between .54 and .74). Sensitivity of the SUS was also demonstrated via significant t-tests on the SUS scores between products. A principal axis factor analysis revealed a one-factor model with mediocre to poor model fit. Overall, the Chinese, French, German and Spanish SUS can be used with confidence to measure the usability of everyday products and systems, and larger sample sizes are required to fully investigate the psychometric properties of the Arabic and Hindi SUS.
Subjective Usability Evaluation: A Comparison of Four Methods
(2018-10-11) Robertson, Ian Wesley; Kortum, Philip T
Subjective usability assessments play a key role in usability research. Several divergent methods of collecting subjective data have developed within usability research literature. This study compared four methods of collective subjective usability data with the System Usability Scale (SUS). Users were asked to use and rate three products with the SUS: a library website, an electric can opener, and a digital timer. Use-Then-Measure, a name applied to usability testing, was used as a reference group to compare the performance of the other three methods. Retrospective usability assessment proved the most promising of those three methods as it generated mean SUS scores that were not statistically distinguishable from the Use-Then-Measure condition. Both the Prospective, judging before use, and Watching-Others, rating products based on video footage, conditions generated mean SUS scores higher than Use-Than-Measure. Retrospective assessment has the most support as an alternative method to usability testing for collecting subjective usability scores. More research is needed to understand if Watching-Others and Prospective methods can be utilized effectively.
System Usability and User Mental Models of Three Verifiable, End-to-end Voting Methods: Helios, Prêt à Voter, and Scantegrity II
(2014-07-11) Acemyan, Claudia Ziegler; Kortum, Philip T; Byrne, Michael D; Lane, David; Wallach, Dan S.
There are many ways voting systems can be maliciously attacked so that election outcomes are altered. In response, voting security experts developed end-to-end (e2e), verifiable voting methods. These systems were intended to be secure, accurate, reliable, and transparent, while still preserving voter anonymity. What is not clear is if these complex, novel systems, which allow voters to check on their ballots after voting, will be usable by every voter. If voting methods are unusable, negative ramifications like disenfranchisement and altered election outcomes could occur. For this reason, system usability and voter mental models of e2e systems must be understood. To address this lacuna in voting research, three e2e methods representative of voter verifiable technologies were studied: Helios, Prêt à Voter, and Scantegrity II. Four studies were conducted. In the first study, baseline usability data was collected. By having participants vote with each system in a mock election, it was found that the systems were difficult, if not impossible, to use. Only 58% of voters were able to cast a ballot, and fewer were able to verify their vote. In the second study, the behavioral errors that led to ballot casting and vote verification event failures were identified, and potential contributing system design deficiencies were discussed. This study revealed that a few design details were driving most of the observed failures, of which all can be fixed. In the third study, voters’ mental models for each voting system were explored. The data supported the claim that voters did not have comprehensive mental models accounting for how the systems work; rather their models emphasized how-to-vote procedures, which were not always correct. In the fourth study it was asked if voters even wanted to use the verification systems, and if they did, what form of verification they would expect. Sixty-five percent of voters indicated that they would be interested in checking that their ballot was cast. As for the preferred form of verification, there was not a consensus—indicating that a diverse set of expectations will need to be accounted for when developing the systems. In conclusion, the tested e2e systems were not easily usable by voters, fully understood by them, or in a form that voters might have expected. Yet the system problems observed can be fixed, and voters seem to support the idea of auditable voting systems—meaning future effort should be spent improving upon the next generations of e2e systems so that all voters can use secure, accurate, transparent, and reliable voting systems.

Browsing by Author "Kortum, Philip T"

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