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Our MODEL OF usability

The International Standards Organisation (ISO) defines usability as “the effectiveness, efficiency and satisfaction" with which a specified set of users can achieve a specified set of tasks in a particular environment” [1]. In our usability studies, we expand on this definition to consider a broad range of factors.

Figure 2: Holistic Model of Usability

[Usefulness][Ease of Use][Satisfaction] [User Experience] [System ContextUser] [Designing for Different User Groups]

USEFULNESS: refers to the effectiveness, efficiency and relevance of the system. Effectiveness refers to the “completeness and accuracy with which users achieve specified goals. It is determined by looking at whether the user’s goals were met successfully and whether all work is correct” [3]. This can be determined by addressing the design rationale and purpose, and whether the design model and system image match the users’ model and expectations [2], and the relevance and accuracy of the content and information. Efficiency refers to the way a system supports users in carrying out their tasks [4], such as, task completion times, optimal navigational paths and click through rates (i.e. number of clicks to completion and sequence) and the number of pages visited in a given period.

EASE OF USE: refers to the navigation, consistency, control, readability and feedback of an interface. Navigation and orientation are critical in the design of usable interfaces, for example: providing visible and alternative methods of navigating such as, consistent and logical menus, embedded links, hotspots, site maps, visual symbols and search tools. Orientation, knowing where you and how to proceed, is achieved by using consistent page layouts, contextual menus, back buttons, link to the home page, progress indicators and status bars. Readability is also important, and this can be achieved by using appropriate terminology and language, fonts, colours, paragraph length, headings, and white space. Users also need relevant and timely feedback in response to their actions, such as confirmation page at the end of a booking process.

SATISFACTION: refers to the users’ perceived enjoyment of system. The overall enjoyment and attitude towards the graphics, colours and layout.

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DIFFERENT USERS: designing for different user groups, such as novice and expert users, children and individuals with disabilities, requires designing interfaces that are accessible, easy to learn and flexible. The Web Accessibility Initiative definition of web accessibility is “access to the web by everyone, regardless of disability” [5]. It is important to design interfaces that have an integrated help system, and use design elements that are familiar and predicable.

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USER EXpERIENCE: observing the user experience can provide a deeper level of understanding of the way users’ interact, perceive and value a real system, such as: exploring social phenomena, such as trust, personal space, safety, security and identity. presence, engagement and immersion are attributes often used to describe virtual spaces and sense of place. Other attributes include: naturalness; sensory perception; orientation and identification; narrative and game play; the use of avatars; and real-world and fantasy representations.

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THE SYSTEM CONTEXT: can be used to describe the context of use, such as, the actual physical environment and social setting, i.e. in a public space, work context or at home. Alternatively, it can refer to the implementation and management of a system and the impact on an organisations culture, collaborative work practices, work flows and processes, standards and policy making.

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Below is a simple model defines the user interface interaction, bewteeen the user, interface and context (Figure 1):

Figure 1: Simple Model of Usability

[User] [Interface] [Context]

USER:
The user has certain characteristics, skills and knowledge that contribute to their interaction and experience of an interface, such as, knowledge of computing, experience of a particular interface; expectations, attitudes and motivations.

INTERFACE:
The interface could be a website; digital media; desktop software; virtual environment and games; ubiquitous and wearable computing; handheld and mobile devices; and kiosks, touch Screens and ATM's.

CONTEXT:
The context describes the purpose and objectives of an interface, i.e. e-commerce website, educational resource or interactive game. The context also describes the physical environment, i.e. use in a public space or in the work place; and the implications on work practice, standards and policy at an organisational or individual level.

 

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