Metrics and Tools to Guide Design of Graphical User Interfaces

User interface design metrics assist developers evaluate interface designs in early phase before delivering the software to end users. This dissertation presents a metric-based tool called GUIEvaluator for evaluating the complexity of the user interface based on its structure. The metrics-model consists of five modified structural measures of interface complexity: Alignment, grouping, size, density, and balance. The results of GUIEvaluator are discussed in comparison with the subjective evaluations of interface layouts and the existing complexity metrics-models. To extend this metrics-model, the Screen-Layout Cohesion (SLC) metric has been proposed. This metric is used to evaluate the usability of user interfaces. The SLC metric has been developed based on Aesthetic, structural, and semantic aspects of GUIs. To provide the SLC calculation, a complementary tool has been developed, which is called GUIExaminer. This dissertation demonstrates the potential of incorporating automated complexity and cohesion metrics into the user interface design process. The findings show that a strong positive correlation between the subjective evaluation and both the GUIEvaluator and GUIExaminer, at a significance level 0.05. Moreover, the findings provide evidence of the effectiveness of the GUIEvaluator and GUIExaminer to predict the best user interface design among a set of alternative user interfaces. In addition, the findings show that the GUIEvaluator and GUIExaminer can measure some usability aspects of a given user interface. However, the metrics validation proves the usefulness of GUIEvaluator and GUIExaminer for evaluating user interface designs

Effet de l’encombrement visuel de l’écran primaire de vol sur la performance du pilote, la charge de travail et le parcours visuel

RÉSUMÉ : Le poste de pilotage d’un avion de ligne du XXIe siècle ne ressemble pas à celui que les frères Wright ont occupé lors de leur premier vol. En effet, la croissance accélérée de l’aviation civile a entrainé une augmentation et une complexification des instruments de vol du poste de pilotage afin de compléter le vol en toute sécurité et dans les temps prévus. Or, présenter au pilote une abondance d’information visuelle par l’entremise d’instruments de vol visuellement encombrés risque de diminuer sa performance de vol. La thématique de l’encombrement visuel des écrans a reçu un intérêt croissant de la communauté aéronautique qui cherche à connaître les effets de la densité et de la surcharge d’information sur le travail des pilotes. La réglementation aérienne demande de minimiser l’encombrement visuel des écrans du poste de pilotage. Les études précédentes sur le sujet ont trouvé un effet mixte de l’encombrement visuel de l’écran primaire de vol sur la performance technique de vol des pilotes. D’autres recherches s’avéraient donc nécessaire pour mieux comprendre ce phénomène. Dans cette thèse, nous avons réalisé une étude expérimentale dans un simulateur de vol afin d’étudier les effets de l’encombrement visuel de l’écran primaire de vol sur la performance du pilote, sa charge mentale de travail et son parcours visuel. Tout d’abord, nous avons identifié une lacune dans les définitions existantes de l’encombrement visuel d’un affichage et nous avons proposé une nouvelle définition pertinente pour le milieu aéronautique qui tient compte du contexte d’utilisation de l’affichage. Ensuite, nous avons montré que les études précédentes sur l’effet de l’encombrement visuel de l’écran primaire de vol sur la performance des pilotes ont mal isolé la variable d’encombrement visuel en manipulant celle-ci en même temps que la fonction de guidage de l’appareil. L’utilisation d’une fonction de guidage différente entre les affichages peut avoir masquée l’effet de l’encombrement visuel sur la performance du pilote. Pour résoudre ce problème, nous avons proposé trois exigences que tous les affichages à l’étude doivent satisfaire afin d’assurer que seule la variable d’encombrement visuelle est manipulée durant l’étude en laissant intouchées les autres variables. Ensuite, nous avons conçu trois écrans primaires de vol ayant un niveau d’encombrement visuel différent (faible, modéré, élevé) mais la même fonction de guidage, en respectant les exigences mentionnées ci-dessus. Douze pilotes, comptant en moyenne plus de 4000 heures de vol, ont complété une approche aux instruments dans un simulateur de vol en utilisant chacun des écrans pour un total de neuf répétitions. Les principaux résultats montrent que les pilotes ont rapporté un niveau de charge mentale de travail inférieure et ont obtenu une meilleure précision latérale durant l’approche en utilisant l’écran ayant un niveau modéré d’encombrement visuel comparativement aux écrans ayant un niveau faible et un niveau élevé d’encombrement visuel. Les pilotes ont aussi jugé que l’écran modérément encombré a été le plus utile pour la tâche de vol comparativement aux deux autres écrans. Les résultats d’oculométrie montrent que l’efficience du parcours visuel du pilote a diminué pour l’écran ayant un encombrement élevé comparativement aux écrans ayant un encombrement faible et un encombrement modéré. Globalement, ces nouveaux résultats expérimentaux révèlent la pertinence d’optimiser l’encombrement visuel des affichages de vol, car il affecte la performance objective et subjective de pilotes expérimentés dans la tâche de vol. La thèse se conclut avec des recommandations pratiques visant à permettre aux concepteurs d’optimiser l’encombrement visuel des écrans dans les interfaces humain-machine.----------ABSTRACT : Flight deck of 21st century commercial aircrafts does not look like the one the Wright brothers used for their first flight. The rapid growth of civilian aviation resulted in an increase in the number of flight deck instruments and of their complexity, in order to complete a safe and on- time flight. However, presenting an abundance of visual information using visually cluttered flight instruments might reduce the pilot’s flight performance. Visual clutter has received an increased interest by the aerospace community to understand the effects of visual density and information overload on pilots’ performance. Aerospace regulations demand to minimize visual clutter of flight deck displays. Past studies found a mixed effect of visual clutter of the primary flight display on pilots’ technical flight performance. More research is needed to better understand this subject. In this thesis, we did an experimental study in a flight simulator to test the effects of visual clutter of the primary flight display on the pilot’s technical flight performance, mental workload and gaze pattern. First, we identified a gap in existing definitions of visual clutter and we proposed a new definition relevant to the aerospace community that takes into account the context of use of the display. Then, we showed that past research on the effects of visual clutter of the primary flight display on pilots’ performance did not manipulate the variable of visual clutter in a similar manner. Past research changed visual clutter at the same time than the flight guidance function. Using a different flight guidance function between displays might have masked the effect of visual clutter on pilots’ performance. To solve this issue, we proposed three requirements that all tested displays must satisfy to assure that only the variable of visual clutter is changed during study while leaving other variables unaffected. Then, we designed three primary flight displays with a different visual clutter level (low, medium, high) but with the same flight guidance function, by respecting the previous requirements. Twelve pilots, with a mean experience of over 4000 total flight hours, completed an instrument landing in a flight simulator using all three displays for a total of nine repetitions. Our results showed that pilots reported lower workload level and had better lateral precision during the approach using the medium-clutter display compared to the low- and high-clutter displays. Also, pilots reported that the medium-clutter display was the most useful for the flight task compared to the two other displays. Eye tracker results showed that pilots’ gaze pattern was less efficient for the high-clutter display compared to the low- and medium-clutter displays. Overall, these new experimental results emphasize the importance of optimizing visual clutter of flight displays as it affects both objective and subjective performance of experienced pilots in their flying task. This thesis ends with practical recommendations to help designers optimize visual clutter of displays used for man-machine interface

Designing for the Cooperative Use of Multi-user, Multi-device Museum Exhibits.

This work explores software-based museum exhibits that allow groups of visitors to employ their own personal mobile devices as impromptu user interfaces to the exhibits. Personal devices commandeered into service in this fashion are dubbed Opportunistic User Interfaces (O-UIs). Because visitors usually prefer to engage in shared learning experiences, emphasis is placed on how to design software interfaces to support collaborative learning. To study the issue, a Design-Based Research approach was taken to construct an externally valid exemplar of this type of exhibit, while also conducting more traditional experiments on specific features of the O-UI design. Three analyses, of – (1) museums as a context, (2) existing computer-based museum exhibits, and (3) computer support of collaborative processes in both work and classroom contexts – produced guidelines that informed the design of the software-based exhibit created as a testbed for O-UI design. The exhibit was refined via extensive formative testing on a museum floor. The experimental phase of this work examined the impact of O-UI design on (1) the visual attention and (2) collaborative learning behaviors of visitors. Specifically, an O-UI design that did not display any graphical output (the “simple” condition) was contrasted against an O-UI design that displayed multi-element, dynamically animated graphics (the “complex” condition). The “complex” O-UIs promoted poor visual attention management, an effect known as the heads-down phenomenon, wherein visitors get so enmeshed with their O-UIs that they miss out on the shared context, to the detriment of group outcomes. Despite this shortcoming, the “complex” O-UIs better promoted goal awareness, on-task interactions between visitors, and equity in participation and performance. The tight output coupling (visitors see only one shared display) of the “simple” O-UI condition promoted emergent competition, and it encouraged some visitors (especially males) to become more engaged than others. Two design recommendations emerge: (1) incorporating devices with private displays (O-UIs with output) as interfaces to a single large display better promotes collaboration (especially equity), and (2) O-UIs with “complex” displays may be used in museum exhibits, but visitors would benefit from mechanisms to encourage them to direct their attention to the shared display periodically.Ph.D.Computer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/61771/1/ltoth_1.pd