A usability evaluation model for accessible mobile e-book applications for the visually impaired

Evaluation plays a critical role in assessing the usability of e-book applications in terms of their accessibility which allows the visually impaired to get the same benefits as ordinary people. However, current e-book usability evaluation models are not for evaluating accessible mobile e-book applications for the visually impaired as they did not sufficiently consider the accessibility issues of these applications. This study aims to develop a model that evaluates the usability of accessible mobile e-book applications for the visually impaired. Literature review and requirement-gathering methods were used to generate usability evaluation factors and metrics and later constructed as a usability evaluation model. This model was verified with 11 domain experts, and the data were analysed using the Fuzzy Delphi Method. Besides, the model was reviewed for consistency, ease of use, understandability, verifiability, and overall impression. Further, a series of online usability tests and interview sessions were conducted with 12 visually impaired participants to validate on data collection ability of the model. The descriptive analysis method was used to analyse objective metrics, and deductive thematic analysis was performed to analyse subjective metrics from interviews. This study initially proposed five evaluation factors: satisfaction, accessibility, efficiency, effectiveness, and learnability, with 35 metrics which were refined to 31 metrics after being verified. Besides, the model was validated, and the findings showed the ability to collect data and the reliability of this model in the actual context of use. The proposed model contributes to the knowledge of accessibility design, evaluation methods and human-computer interaction. Mobile application developers or usability researchers can use this model as one of the references for developing excellent and usable accessible mobile e-book applications for the visually impaired. By having a usable and satisfying accessible mobile e-book application, visually impaired learning and reading routines could be more accessible