Usability and User Experience, Vol. 156, 2024, 65–77 https://doi.org/10.54941/ahfe1005416 The Relevancy of Knowledge and the Knowledge of Relevancy: An Information Theory-Based Quantitative Methodology for Evaluating UI Design and Usability Lance Chong University of Lethbridge, Alberta, Canada ABSTRACT Usability evaluation has posed a complex challenge for several decades. Given its importance, there is a pressing need for fundamental theoretical advancements. This paper introduces a novel approach by formulating a set of information theory-based methodologies for the quantitative and more direct evaluation of user interface (UI) design and usability. These methodologies are encapsulated within the new the- oretical framework of Networked Two-Way Communication Channels (NTCC). This framework extends Claude Shannon’s original one-directional communication chan- nel model by incorporating the user’s active involvement in the user-to-UI interac- tion processes. The NTCC model shows promise for mathematically modeling the mechanisms of user-to-UI interactions and providing more direct assessments of UI usability. Keywords: Usability, Information theory, Human-computer interaction (HCI), User interface (UI), User experience (UX), Human-centered design, Design evaluation, Interface entropy, Inter- face temperature, Thermodynamics in UI, NTCC model (networked two-way communication channels) INTRODUCTION The widely accepted definition of “usability” is often regarded as an elusive “general concept that cannot be directly measured” (Nielsen, 1994). There- fore, indirect parameters need to be used to evaluate user interfaces (UIs) and other products’ usability. Indeed, the features of a UI, the motivations of the user, and countless other factors can influence the interaction process. Each parameter can potentially encompass an infinite range of complexity. However, given that such complex subjects have been successfully studied in many well-established fields of science, it is conceivable that if the young field of UI design and research is to become a matured science, its theoretical foundation might eventually resemble that of other more established fields of science. Two scientific fields with noticeable similarities are information theory and thermodynamics. Following long-standing scientific conventions, each of these two branches of science shares the commonality of approach- ing old research problems from new and detached perspectives. Both utilize © 2024. Published by AHFE Open Access. All rights reserved. 65