Usability


Usability or user friendliness can be described as the capacity of a system to provide a condition for its users to perform the tasks safely, effectively, and efficiently while enjoying the experience. In software engineering, usability is the degree to which a software can be used by specified consumers to achieve quantified objectives with effectiveness, efficiency, and satisfaction in a quantified context of use.
The object of use can be a software application, website, book, tool, machine, process, vehicle, or anything a human interacts with. A usability study may be conducted as a primary job function by a usability analyst or as a secondary job function by designers, technical writers, marketing personnel, and others. It is widely used in consumer electronics, communication, and knowledge transfer objects and mechanical objects such as a door handle or a hammer.
Usability includes methods of measuring usability, such as needs analysis and the study of the principles behind an object's perceived efficiency or elegance. In human-computer interaction and computer science, usability studies the elegance and clarity with which the interaction with a computer program or a web site is designed. Usability considers user satisfaction and utility as quality components, and aims to improve user experience through iterative design.

Introduction

The primary notion of usability is that an object designed with a generalized users' psychology and physiology in mind is, for example:
  • More efficient to use—takes less time to accomplish a particular task
  • Easier to learn—operation can be learned by observing the object
  • More satisfying to use
Complex computer systems find their way into everyday life, and at the same time the market is saturated with competing brands. This has made usability more popular and widely recognized in recent years, as companies see the benefits of researching and developing their products with user-oriented methods instead of technology-oriented methods. By understanding and researching the interaction between product and user, the usability expert can also provide insight that is unattainable by traditional company-oriented market research. For example, after observing and interviewing users, the usability expert may identify needed functionality or design flaws that were not anticipated. A method called contextual inquiry does this in the naturally occurring context of the users own environment. In the user-centered design paradigm, the product is designed with its intended users in mind at all times. In the user-driven or participatory design paradigm, some of the users become actual or de facto members of the design team.
The term user friendly is often used as a synonym for usable, though it may also refer to accessibility. Usability describes the quality of user experience across websites, software, products, and environments. There is no consensus about the relation of the terms ergonomics and usability. Some think of usability as the software specialization of the larger topic of ergonomics. Others view these topics as tangential, with ergonomics focusing on physiological matters and usability focusing on psychological matters. Usability is also important in website development. According to Jakob Nielsen, "Studies of user behavior on the Web find a low tolerance for difficult designs or slow sites. People don't want to wait. And they don't want to learn how to use a home page. There's no such thing as a training class or a manual for a Web site. People have to be able to grasp the functioning of the site immediately after scanning the home page—for a few seconds at most." Otherwise, most casual users simply leave the site and browse or shop elsewhere.
Usability can also include the concept of prototypicality, which is how much a particular thing conforms to the expected shared norm, for instance, in website design, users prefer sites that conform to recognised design norms.

Definition

defines usability as "The extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency, and satisfaction in a specified context of use." The word "usability" also refers to methods for improving ease-of-use during the design process. Usability consultant Jakob Nielsen and computer science professor Ben Shneiderman have written about a framework of system acceptability, where usability is a part of "usefulness" and is composed of:
  • Learnability: How easy is it for users to accomplish basic tasks the first time they encounter the design?
  • Efficiency: Once users have learned the design, how quickly can they perform tasks?
  • Memorability: When users return to the design after a period of not using it, how easily can they re-establish proficiency?
  • Errors: How many errors do users make, how severe are these errors, and how easily can they recover from the errors?
  • Satisfaction: How pleasant is it to use the design?
Usability is often associated with the functionalities of the product, in addition to being solely a characteristic of the user interface. For example, in the context of mainstream consumer products, an automobile lacking a reverse gear could be considered unusable according to the former view, and lacking in utility according to the latter view. When evaluating user interfaces for usability, the definition can be as simple as "the perception of a target user of the effectiveness and efficiency of the Interface". Each component may be measured subjectively against criteria, e.g., Principles of User Interface Design, to provide a metric, often expressed as a percentage. It is important to distinguish between usability testing and usability engineering. Usability testing is the measurement of ease of use of a product or piece of software. In contrast, usability engineering is the research and design process that ensures a product with good usability. Usability is a non-functional requirement. As with other non-functional requirements, usability cannot be directly measured but must be quantified by means of indirect measures or attributes such as, for example, the number of reported problems with ease-of-use of a system.

Intuitive interaction or intuitive use

The term intuitive is often listed as a desirable trait in usable interfaces, sometimes used as a synonym for learnable. In the past, Jef Raskin discouraged using this term in user interface design, claiming that easy to use interfaces are often easy because of the user's exposure to previous similar systems, thus the term 'familiar' should be preferred. As an example: Two vertical lines "||" on media player buttons do not intuitively mean "pause"—they do so by convention. This association between intuitive use and familiarity has since been empirically demonstrated in multiple studies by a range of researchers across the world, and intuitive interaction is accepted in the research community as being use of an interface based on past experience with similar interfaces or something else, often not fully conscious, and sometimes involving a feeling of "magic" since the course of the knowledge itself may not be consciously available to the user. Researchers have also investigated intuitive interaction for older people, people living with dementia, and children.
Some have argued that aiming for "intuitive" interfaces could lead designers to discard a better design solution only because it would require a novel approach and to stick with boring designs. However, applying familiar features into a new interface has been shown not to result in boring design if designers use creative approaches rather than simple copying. The throwaway remark that "the only intuitive interface is the nipple; everything else is learned." is still occasionally mentioned. Any breastfeeding mother or lactation consultant will tell you this is inaccurate and the nipple does in fact require learning on both sides. In 1992, Bruce Tognazzini even denied the existence of "intuitive" interfaces, since such interfaces must be able to intuit, i.e., "perceive the patterns of the user's behavior and draw inferences." Instead, he advocated the term "intuitable," i.e., "that users could intuit the workings of an application by seeing it and using it". However, the term intuitive interaction has become well accepted in the research community over the past 20 or so years and, although not perfect, it should probably be accepted and used.

ISO standards

ISO/TR 16982:2002 standard

ISO/TR 16982:2002 is an International Standards Organization standard that provides information on human-centered usability methods that can be used for design and evaluation. It details the advantages, disadvantages, and other factors relevant to using each usability method. It explains the implications of the stage of the life cycle and the individual project characteristics for the selection of usability methods and provides examples of usability methods in context. The main users of ISO/TR 16982:2002 are project managers. It therefore addresses technical human factors and ergonomics issues only to the extent necessary to allow managers to understand their relevance and importance in the design process as a whole. The guidance in ISO/TR 16982:2002 can be tailored for specific design situations by using the lists of issues characterizing the context of use of the product to be delivered. Selection of appropriate usability methods should also take account of the relevant life-cycle process. ISO/TR 16982:2002 is restricted to methods that are widely used by usability specialists and project managers. It does not specify the details of how to implement or carry out the usability methods described.

ISO 9241 standard

is a multi-part standard that covers a number of aspects of people working with computers. Although originally titled Ergonomic requirements for office work with visual display terminals , it has been retitled to the more generic Ergonomics of Human System Interaction. As part of this change, ISO is renumbering some parts of the standard so that it can cover more topics, e.g. tactile and haptic interaction. The first part to be renumbered was part 10 in 2006, now part 110.