Prioritizing usability problems: data-driven and judgement-driven severity estimates

Software-ergonomic system analysis often reveals numerous usability problems. Given that system design suffers from limited resources, the prioritization of usability problems seems inevitable. Surprisingly enough, prioritization is not in the focus of scientific interest. Within this paper, approaches to prioritization relying on severity estimates will be presented. Two of the approaches, namely priorities based on data about the impact of a problem (data-driven) and priorities based on judgements of interest group members (judgement-driven) will be further explored. In the data-driven approach total problem-handling time caused by a usability problem is presented as a measure of severity. The major disadvantage of the data-driven approach is its costs. A possible alternative are severity estimates based on judgements by members of involved interest groups. The first of two studies shows how to obtain judgement driven severity estimates and reveals a fundamental lack of correspondence between data-driven and judgement-driven severity estimates. The second study supports the notion that the lack of correspondence may stem from a difference between assumptions of the data-driven approach and the naive judgement model of interest group members in the judgement-driven approach. A hypothetical model for severity estimates by interest group members is presented.     

The Inference of Perceived Usability From Beauty

A review of 15 papers reporting 25 independent correlations of perceived beauty with perceived usability showed a remarkably high variability in the reported coefficients. This may be due to methodological inconsistencies. For example, products are often not selected systematically, and statistical tests are rarely performed to test the generality of findings across products. In addition, studies often restrict themselves to simply reporting correlations without further specification of underlying judgmental processes.

The present study's main objective is to re-examine the relation between beauty and usability, that is, the implication that “what is beautiful is usable.” To rectify previous methodological shortcomings, both products and participants were sampled in the same way and the data aggregated both by averaging over participants to assess the covariance across ratings of products and by averaging over products to assess the covariance across participants. In addition, we adopted an inference perspective to qualify underlying processes to examine the possibility that, under the circumstances pertaining in most studies of this kind where participants have limited experience of using a website or product, the relationship between beauty and usability is mediated by goodness.

A mediator analysis of the relationship between beauty, the overall evaluation (i.e., “goodness”) and pragmatic quality (as operationalization of usability) suggests that the relationship between beauty and usability has been overplayed as the correlation between pragmatic quality and beauty is wholly mediated by goodness. This pattern of relationships was consistent across four different data sets and different ways of data aggregation. Finally, suggestions are made regarding methodologies that could be used in future studies that build on these results.     

Reconstructing experiences with iScale

We present iScale, a survey tool for the retrospective elicitation of longitudinal user experience data. iScale aims to minimize retrospection bias and employs graphing to impose a process during the reconstruction of one's experiences. Two versions, the constructive and the value-account iScale, were motivated by two distinct theories on how people reconstruct emotional experiences from memory. These two versions were tested in two separate studies. Study 1 aimed at providing qualitative insight into the use of iScale and compared its performance to that of free-hand graphing. Study 2 compared the two versions of iScale to free recall, a control condition that does not impose structure on the reconstruction process. Overall, iScale resulted in an increase in the amount, the richness, and the test–retest consistency of recalled information as compared to free recall. These results provide support for the viability of retrospective techniques as a cost-effective alternative to longitudinal studies.     

Thin windows for gaseous and liquid targets: An optimization procedure

Many nuclear physics experiments require cryogenic or high-pressure gas targets with thin windows. To obtain the best data, that is, to reduce background signals, a target window would ideally have zero thickness and zero deflexion. Since this is not possible a trade-off is made among target geometry, window geometry, window material, and window thickness. Measurements of deflexions of a variety of window materials and geometries were performed at room temperature and in liquid nitrogen to aid window design in the future. A simple graphical method for predicting the rupture pressure for several typical window materials is described. The results of the deflexion measurements are compared to a finite element computer programme Membran which predicts window deflexion and material stresses for a uniform applied pressure.     

The dilemma of the hedonic - Appreciated, but hard to justify

With the experiential turn in Human-Computer Interaction (HCI), academics and practitioners broaden their focus from mere task-fulfillment (i.e., the pragmatic) to a holistic view, encompassing universal human needs such as relatedness or popularity (i.e., the hedonic). Accordingly, many theoretical models of User Experience (UX) acknowledge the hedonic as an important aspect of a product’s appeal. In choice situations, however, people (i.e., users, consumers) overemphasize the pragmatic, but fail to acknowledge the hedonic. The present research explores the reasons for this phenomenon. We suggest that people attend to the justifiability of hedonic and pragmatic attributes rather than to their impact on experience. In other words, they choose what is easy to justify and not what they enjoy the most. Since providing justifications is easier for pragmatic than hedonic attributes, people arrive at a primarily pragmatic choice, even if they would feel better with the hedonic. We explored this assumption, called the Hedonic Dilemma, in four empirical studies. Study 1 (N = 118) revealed a positive correlation between the need for justification and pragmatic choice. Study 2 (N = 125) explored affective consequences and justifications provided for hedonic and pragmatic choices. We further explored two different ways to reduce the Hedonic Dilemma. Study 3 (N = 178) enhanced the justifiability of hedonic choice through product information which suggested hedonic attributes as legitimate. In consequence, hedonic choice increased. Study 4 (N = 133) manipulated the need for justification through framing the choice context. A significant positive effect of a “low need for justification” frame on purchase rates occurred for a hedonic but not for a pragmatic product. Our research has a number of implications, reaching from how to elicit requirements to general strategic considerations when designing (for) experiences.     

Superconducting magnetic energy storage

Superconducting magnetic energy storage (SMES) is an energy storage technology that stores energy in the form of DC electricity that is the source of a DC magnetic field. The conductor for carrying the current operates at cryogenic temperatures where it is a superconductor and thus has virtually no resistive losses as it produces the magnetic field. The overall technology of cryogenics and superconductivity today is such that the components of a SMES device are defined and can be constructed. The integrated unit appears to be feasible for some utility applications at a cost that is competitive with other technologies. SMES is the only technology based on superconductivity that is applicable to the electric utilities and is commercially available today. In addition to today's power quality application, the historical development of SMES starting with the concept of very large plants that would store hundreds of megawatt hours of energy and were intended for diurnal load leveling are described.     

Design of epoxy-free superconducting dipole magnets and performance in both Helium I and pressurized Helium II

Three model superconducting dipole magnet 1m long, without iron, having a bore diameter of 76 mm have been built without epoxy resins or other adhesives and tested in He I and He II. The conductor is the 23-strand Rutherford-type cable used in the Fermilab Doubler Saver magnets, and is insulated with Mylar and Kapton. The two-layer winding is highly compressed by a system of structural support rings and tapered collets. Little "training" was required to reach quench currents greater than 95 percent of "short sample" in Helium I. The maximum quench current in He II is increased 20 to 30 percent, compared with He I operation at 4.4 K. Test results are given on cyclic losses, heater-induced quenches, and charge-rate effects.     

Capturing Design Space From a User Perspective: The Repertory Grid Technique Revisited

The design of an artifact (e.g., software system, household appliance) requires a multitude of decisions. In the course of narrowing down the design process, "good ideas" have to be divided from "bad ideas." To accomplish this, user perceptions and evaluations are of great value. The individual way people perceive and evaluate a set of prototypes designed in parallel may shed light on their general needs and concerns. The Repertory Grid Technique (RGT) is a method of elucidating the so-called personal constructs (e.g., friendly-hostile, bad-good, playful-expert-like) people employ when confronted with other individuals, events, or artifacts. We assume that the personal constructs (and the underlying topics) generated as a reaction to a set of artifacts mark the artifacts' design space from a user's perspective and that this information may be helpful in separating valuable ideas from the not so valuable. This article explores the practical value of the RGT in gathering design-relevant information about the design space of early artifact prototypes designed in parallel. Ways of treating the information gathered, its quality and general advantages, and limitations of the RGT are presented and discussed. In general, the RGT proved to be a valuable tool in exploring a set of artifact's design space from a user's perspective.     

Using behavioral patterns to assess the interaction of users and product

We hypothesized that users show different behavioral patterns at work when using interactive products, namely execute, engage, evolve and expand. These patterns refer to task accomplishment, persistence, task modification and creation of new tasks, each contributing to the overall work goal. By developing a questionnaire measuring these behavioral patterns we were able to demonstrate that these patterns do occur at work. They are not influenced by the users alone, but primarily by the product, indicating that interactive products indeed are able to support users at work in a holistic way. Behavioral patterns thus are accounted for by the interaction of users and product.