Meeting the increasing demand for desktop-like applications on mobile products requires powerful interaction techniques. One candidate is GUI-style point-andclick interaction using an integrated pointing device that supports handheld use. We tested an isometric joystick for this purpose. Two prototypes were built. They were designed for thumb operation and included a separate selection button. Twelve participants performed point-and-select tasks. We tested both one-handed and two-handed interaction, and selection using the separate selection button and the joystick's integrated press-toselect feature. A notebook configuration served as a reference. Results for the handheld conditions, both one-handed and two-handed, were just slightly off those for the notebook condition, suggesting that an isometric joystick is suitable as a pointing device for handheld terminals. Inadvertent selection while moving the pointer yielded high error rates for all conditions using press-to-select. A separate select button is therefore needed to ensure accurate selection. Key words: Isometric joystick, pointing devices, handheld devices, ISO 9241, Fitts' law. 1

Current methods to represent system or task usability in a single metric do not include all the ANSI and ISO defined usability aspects: effectiveness, efficiency & satisfaction. We propose a method to simplify all the ANSI and ISO aspects of usability into a single, standardized and summated usability metric (SUM). In four data sets, totaling 1860 task observations, we show that these aspects of usability are correlated and equally weighted and present a quantitative model for usability. Using standardization techniques from Six Sigma, we propose a scalable process for standardizing disparate usability metrics and show how Principal Components Analysis can be used to establish appropriate weighting for a summated model. SUM provides one continuous variable for summative usability evaluations that can be used in regression analysis, hypothesis testing and usability reporting. ACM Classification

Abstract. Understanding how to implement SPI successfully is arguably the most challenging issue facing the SPI field today. The SPI literature contains many case studies of successful companies and descriptions of their SPI programs. However, there has been no systematic attempt to synthesize and organize the prescriptions offered. The research efforts to date are limited and inconclusive and without adequate theoretical and psychometric justification. This paper provides a synthesis of prescriptions for successful quality management and process improvement found from an extensive review of the quality management, organizational learning, and software process improvement literature. The literature review was confirmed by empirical studies among both researchers and practitioners. The main result is an instrument for measuring the key factors of success in SPI based on data collected from 120 software organizations. The measures were found to have satisfactory psychometric properties. Hence, managers can use the instrument to guide SPI activities in their respective organizations and researchers can use it to build models to relate the facilitating factors to both learning processes and SPI outcomes.

Factor analysis is a method in multivariate statistical analysis that can help scientists determine which variables to study in a field and their relationships. We extend the Bayesian approach to factor analysis developed in 1989 by Press and Shigemasu (henceforth PS89) and revised in 1997 to model correlated observation vectors, factor score vectors, and factor loadings. Further, we place a prior distribution on the number of factors and obtain posterior estimates. Hitherto,

The most common form of dataset within the educational domain is likely the course gradebook. Data mining on the assignment-level scores is unlikely to provide meaningful results, but a matrix recording scores for every student and every question may provide hidden insight into the workings of a course. Here we will investigate collaborative filtering techniques applied to such data in an attempt to discover what the fundamental topics of a course are and the proficiencies of each student in those topics. Nearly every university-level course offering creates a new education-related dataset in the process of recording student grades. While the vast majority of gradebooks record each student’s aggregate score on each assignment,

Consistent with the conceptualizations of participation and involvement in psychology, organizational behavior, consumer behavior, and other disciplines, this paper redefines the participation construct to distinguish its. behavioral and psychological dimensions. "User participation " is defined as the observable behavior of information system users in the information system development process; "user involvement " as a need-based attitude orpsychological state of users with regard to that process and to the resultant information system; and "user engagement " as the set of user behaviors and attitudes toward information systems and their development. A field study was conducted in a $40 billion interstate bank during the installation and conversion of an information system. A questionnaire was developed, pre-tested, and validated for internal consistency, temporal stabfity, factorial validity, and multicollinearity. Path analysis was used for theory testing (i.e., model comparison). There was strong empirical evidence to support: (1) that user involvement is something distinct from, although associated wit4 user participation; (2) that this psychological state of user involvement may be more important than user participation in understanding information system success; (3) that the behavioral-attitudinal theory of information system success @e., that participation "causes " involvement which mediates the participation-success relationship) is superior to the behavioral theory (i.e., participation "causes " success); and (4) that user engagement during the installation phase is strongly associated with user satisfaction. 1.

Drought is the most economically expensive recurring natural disaster to strike North America in modern times. Recently available gridded drought reconstructions have been developed for most of North America from a network of drought-sensitive tree-ring chronologies, many of which span the last 1000 yr. These reconstructions enable the authors to put the famous droughts of the instrumental record (i.e., the 1930s Dust Bowl and the 1950s Southwest droughts) into the context of 1000 yr of natural drought variability on the continent. We can now, with this remarkable new record, examine the severity, persistence, spatial signatures, and frequencies of drought variability over the past milllennium, and how these have changed with time. The gridded drought reconstructions reveal the existence of successive “megadroughts, ” unprecedented in persistence (20–40 yr), yet similar in year-to-year severity and spatial distribution to the major droughts experienced in today’s North America. These megadroughts occurred during a 400-yr-long period in the early to middle second millennium A.D., with a climate varying as today’s, but around a drier mean. The implication is that the mechanism forcing persistent drought in the West and the Plains in the instrumental era is analagous to that underlying the megadroughts of the medieval period. The leading spatial mode of

Abstract. Proposed in response to the growing number of passwords users have to memorize, password managers allow to store one’s credentials, either on a third-party server (online password manager), or on a portable device (portable password manager) such as a mobile phone or a USB key. In this paper, we present a comparative usability study of three popular password managers: an online manager (LastPass), a phone manager (KeePassMobile) and a USB manager (Roboform2Go). Our study provides valuable insights on average users ’ perception of security and usability of the three password management approaches. We find, contrary to our intuition, that users overall prefer the two portable managers over the online manager, despite the better usability of the latter. Also, surprisingly, our non-technical pool of users shows a strong inclination towards the phone manager. These findings can generally be credited to the fact that the users were not comfortable giving control of their passwords to an online entity and preferred to manage their passwords themselves on their own portable devices. Our results prompt the need for research on developing user-friendly and secure phone managers, owing to the ubiquity of mobile phones. 1

Abstract—Internet traffic primarily consists of packets from elastic flows, i.e., Web transfers, file transfers, and e-mail, whose transmissions are mediated via the Transmission Control Protocol (TCP). In this paper, we develop a methodology to process TCP flow measurements in order to analyze throughput correlations among TCP flow classes that can be used to infer congestion sharing in the Internet. The primary contributions of this paper are: 1) development of a technique for processing flow records suitable for inferring congested resource sharing; 2) evaluation of the use of factor analysis on processed flow records to explore which TCP flow classes might share congested resources; and 3) validation of our inference methodology using bootstrap methods and nonintrusive, flow level measurements collected at a single network site. Our proposal for using flow level measurements to infer congestion sharing differs significantly from previous research that has employed packet level measurements for making inferences. Possible applications of our method include network monitoring and root cause analysis of poor performance. Index Terms—Factor analysis, inference of congestion sharing, network measurement. I.

BGP updates are triggered by a variety of events such as link failures, session resets, router crashes, policy or configuration changes. Making sense of BGP update streams and inferring their underlying causes is important in trouble-shooting BGP and improving its performance. In this paper we propose a novel methodology to identify BGP updates associated with major events – affecting network reachability to multiple ASes – and separating them (statistically) from those attributable to minor events, which individually generate few updates, but collectively form the persistent background noise observed at BGP vantage points. Our methodology is based on principal component analysis (PCA), which enables us to transform and reduce the BGP updates into different AS clusters that are likely affected by distinct major events. We also perform “spatial correlation ” and “type-of-change ” analysis based on AS PATH attributes to further validate and corroborate our findings. We demonstrate the accuracy and effectiveness of our methodology through simulations, and subsequently apply it to real BGP data. In addition, we corroborate our approach by analyzing updates corresponding to periods in which well-known routing events took place. I.