1995 18 23 usability attributes it is imperative to

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Unformatted text preview: ould be designed to match their requirements” (Preece et al.,1995). 18 2.3 Usability Attributes It is imperative to understand that usability is not a single, one-dimensional property of a user interface. According to Nielsen (1993) usability has multiple, components and it is traditionally associated with these five usability attributes: 1) 2) 3) 4) 5) Learnability Efficiency of use Memorability Few and non-catastrophic errors and Subjective satisfaction. Below, we will discuss all attributes in details. 2.3.1 Learnability According to Nielsen (1993) the system should be easy to learn so that the user can rapidly start getting some work done with the system. Learnability is most likely the fundamental usability attribute as most systems need to be easy to learn, since the first experience of users it to learn and understand the system. Although, there are some certain ways to train the user how to learn system but as general systems needs to be easy to learn and understand. The initial ease of learning is most likely the easiest of the usability attributes to measure with the exception of subjective satisfaction. We can take some novice users to test any system and can measures the time they takes to reach a specified level of proficiency in using that system. However, these test users should be future users of that system. The easiest and most common way to express their proficiency is simply to state that the users have to be able to complete a certain task successfully. As an alternative, one can specify that users need to be able to complete a set of tasks in a certain, minimum time before one will consider them that they have learned that system. (Nielsen 1993) 2.3.2 Efficiency of Use: In order to ensure a high level of productivity, the systems should be efficient to use, so that once the user has learned the system they can easily use it. System efficiency refers to the stable performance stage of expert user. Different systems have different level of efficiency of use, for instance some operating systems are very much complex to understand and take couple of months to reach an efficiency level. (Nielsen 1993) 19 Experience is the key to measure efficiency; therefore efficiency can be measured with the help of experienced users. Experience can be defined with the help of users who have been operating a system for some specific period of time i.e. some months or years. In addition, experience can also be defined in terms of number of hours spent using the system. A test case was conducted to measure efficiency, test users are asked to use the system for a certain number of hours, after which finally it is possible to define test users as expert users. In addition, efficiency of use can be measured by taking a group of users and test a system based on some specific tasks and when the expertise of users will reach to a certain level they would be declared as “experience” users. (Nielsen 1993) 2.3.3 Memorability: According to Nielsen (1993) memorability is referred that a system should be easy to remember, so that a formal user is able to return to the system after some period without having to relearn everything over again. Casual users are the third major category of users along with the beginner/novice and expert users. Casual users are such users who are use a system occasionally as compare to expert users. As compare to the novice users, casual users have used a system before therefore they do not need to learn it from scratch; they just need to remember how to use it based on their previous knowledge. This causal use is generally concern with utility programs that are just used in few and for between. However, some other program like quarterly report and annual reports making is also falls in this category. Easy to remember interface is also vital for users who return after vacation or who have temporarily stopped using a program. Improvements in learnability often make an interface easy to remember; however, principally the usability of returning to a system is different from that of facing it for the first time. (Nielsen 1993) As compare to other usability features, interface memorability measurement have rarely been tested in detail. Interface memorability test could be perform with any casual user who have been out of touch from the system for a specific amount of time and measure the time he need to perform some typical test task on the previously used system. Alternatively, it is also possible to conduct a memory test with users after they finished a test session with the system and ask them to explain the effect of various commands. The interface score for memorability will be the number of correct answers given by those casual users. (Nielsen 1993) 2.3.4 Few and non-catastrophic Errors: An error can be defined as, any action that does not accomplish the desired goal. The system’s error rate can be measured by counting the number of such actions made by 20 system users while performing some particular tasks. Accordingly, system error rates can be mea...
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