PaUSABILITY
Definition
Standard description in 1998, a standard description perhaps was the one generated in the ISO9241 (International Standards Organization) as enablers in achieving a specified goals in terms of the characteristics of hardware, software and organizational environment that promote ergonomic and usability principles (Bevan, 2001). ISO9241-11(1998) explained usability as measuring the way vendors and workers tend to achieve cost-effectiveness, efficiency and user requirements and satisfaction in a specified context of use within the confines of the environment.
Table 2.1
Classification of All the features in the ISO description of Usability (ISO 9241-11 1998)
Features Explanation
Effectiveness the precision and totality of meeting organisational needs and
Efficiency availability of scarce the resources required to achieve goals.
Satisfaction Independent from strain, anxiety and confidence in using
The product or ease of use of product
Context of use the users, tasks, equipment including hardware, software and
Materials and the physical and social interactions in which a
Product is used
Work System the structure, which involve users, equipment, tasks, physical sci and social environment in accomplishing organizational goals
As well as the context of use of products
User End users or persons authorised to use the product
Goal Result of implemented system
Task the operational activities of the implemented systems and their
Social, physical and cognitive interactions.
Product service and items (hardware, software and materials)
With usability specifications and evaluations
Measure Describing how organisational and user requirements
Have been achieved as well as time restrictions, example heuristic
Evaluation and performance testing
For the purposes of this research, the ISO 9241-11 standard definition is used with reference to Nielsen’s five attributes of learnability, efficiency, memorability, errors and satisfaction will be explain in details concerning usability of health information systems.
The usability goals, which focus on the last two traits, lead to more practical evaluation: Learnability, efficiency, rate of errors, memorability and user satisfaction. The utopian goal would be for all user interfaces to be excellent at all these attributes. However, the reality is that designers need to make trade-offs in user interface design.
Learnability explains how easy the system is to learn. It inadvertently emphasises users’ ability to reach a sufficient skill level in accomplishing task. A well-organised system with good learnability will give a steep learning curve. Typically, the learning curve starts at zero, which means that the user is not able to use e.g. a health information system the first time trying. A steep curve indicates fast understanding and ability to gain information from the system. Learnability is in many cases the most important usability attributes because the first assignment the user has with any new system is to learn to use it (Nielsen, 1994).
A learning curve illustrates the pace of learning from a novice user to skilled user. With repetition of a task, a user will increase the speed and performance in a task over time. Learning generally happens more quickly in the beginning and a after a while reaches a plateau, which means learning happens at a slower pace (Ritter & Schooler, 2001).
Memorability is defined as ease of use of the system and ability of the system is to remember. Systems with good memorability are easy to get back to after not having used the system for some time. Memorability also refers to ease of use of the system encouraging unintended users to relearn and accomplish task they only use occasionally. These users do not have to learn the interface from scratch (Nielsen, 1994). An example of an interface element that is hard to learn but easy to remember is the method of closing applications in an IOS 7 Apple device (e.g. IPhone). This concept is not easy to understand the first time you see it, but when you have learned it, it is probable that you will remember it the next time you want to close something.
Rate of errors refer to how many mistakes a user will commit per unit of time using a system and how easy it is to recover from them. According to a common definition, an error is “any action that does not accomplish the desired goal” and one can measure the error rate by counting the “number of Efficiency Time Page 36 of 97 errors that a user makes when performing a specified task” (Nielsen, 1994). Errors can of course be more or less serious. Errors that cause failure to complete the work or errors that are difficult to discover and lead to flaws in the work must be minimized in the system. Smaller errors that just slow the user down are more acceptable (Nielsen, 1994)
User Satisfaction explains ease of accomplishing task and the users ‘interaction of the system – i n other words how likeable the system is. This category is most important for recreational software like painting software or games as these activities are mainly motivated by subjective positive perception. Efficiency is not always a goal in these systems, the fun factor is more important. The field of creating compelling user interfaces is known as Human Computer Interaction. It mainly consists of computer science and experimental psychology. Human Computer Interaction also integrates lessons from ergonomics, sociology, anthropology education industrial psychology, instructional and graphic design, technical writing and other domains (Shneiderman, Plaisant, Cohen, & Jacobs, 2009).
According to Nielsen there are three main dimensions of how user experience with a system differs from person to person (Nielsen, 1994). One of the dimensions is how much computer experience the user has, which can range from minimal to extensive. The next dimension is how skilled the user is with one particular system, which ranges from novice to expert. The third dimension is how knowledgeable the user is with the software’s subject domain. For example, in a word processing software, a person needs to have knowledge i n the domain of how to format a document as well as skills in the particular word processor, to format a document correctly. In order to learn the skills on how to operate a particular system, one needs to have a certain amount of computer experience. In one particular example, the first dimension would be the skills needed to turn on the computer and open the word processor. The second dimension would be to use the word processor to create and format a document and the third dimension would be knowledge in the subject t matter to write about.
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