Usability Concepts and Terms

What is Usability?

Usability is the degree to which a system is easy to use or user-friendly. It can also refer to a method of measuring and testing user friendliness or user-centered design. Design addressing the five facets of usability can increase the acceptance rate of a new technology (Nielsen, 1994). These facets are:

Learnability: The system should be easy to learn so the user can rapidly catch on.
Efficiency: A measure of how productive a user is once he/she has learned the system.
Memorability: Ability of a system’s ease to remember; even the intermittent or casual user should be able to return to the system after some period of not having used it, without having to learn everything all over again.
Errors: A system should have a low error rate, so users make few errors during the use of the system, and, if they do make errors, they can easily be corrected.
Satisfaction: The user should consider the system pleasant to use in order to subjectively determine if they like it.

What is Participatory Ergonomics?

Participatory Ergonomics is a method in which non-experts in ergonomics are trained by ergonomics experts through a continuous information exchange (e.g., training). The goal of the information exchange is to put in place a program within an organization that relies on the active involvement of the newly trained experts. These individuals then use their newly-acquired knowledge and skills to identify, design and implement ergonomic solutions within the organization, ultimately without the aid of the ergonomic experts.

What is Heuristic Evaluation?
A heuristic evaluation is a generally informal means of design assessment (e.g., of a technology) based on generally recognized rules of thumb or principles of design.

What are the Nielsen – Schneiderman heuristics (Zhang et al, 2003) of computer-interface design?

Consistency: Users should not have to wonder whether different words, situations, or actions mean the same thing. Standards & conventions should be followed.
Visibility: Users should be informed about what’s going on with the systems through appropriate feedback & display of information.
Match: The image of the system perceived by the users should match the model the users have about the system.
Minimalist: Any extraneous information is a distraction & slow-down.
Memory: Users should not have to be required to memorize a lot of information to carry out tasks.
Feedback: Users should be given prompt & informative feedback.
Flexibility: Users always learn & users are different. Give users the flexibility to create customization & shortcuts to accelerate their performance.
Message: The messages should be informative enough such that users can understand the nature of errors, learn from errors & recover from them.
Error: It is always better to design interfaces that prevent errors from happening in the first place.
Closure: Every task has a beginning and an end. Users should be clearly notified about the completion of a task.
Undo: Users should be allowed to recover from errors. Reversible actions also encourage exploratory learning.
Language: The language utilized should always be presented in a form understandable by the intended users.
Control: Do not give users that impression that they are controlled by the system.
Document: Always provide help when needed.