Usability refers to how well users can learn and use a product to achieve their goals and how satisfied they are with that process. The key methodology for carrying out usability is called User-Centered Design, which is an approach for employing usability. It is a structured product development methodology that involves users throughout all stages of website development, in order to create a website that meets users' needs. Usability means the quality of a user's experience when interacting with a product or system- whether a website, a software application, mobile technology, or any user-operated device. Usability is a combination of factors including:
Ease of learning- how fast can a user who has never seen the user interface before learn it sufficiently well to accomplish basic tasks?
Efficiency of use- Once an experienced user has learned to use the system, how fast can he or she accomplish tasks?
Memorability- If a user has used the system before, can he or she remember enough to use it effectively the next time or does the user have to start over again learning everything?
Subjective satisfaction- How much does the user like using the system?
The most common factors measured in usability testing include:
Effectiveness- A users's ability to successfully use a website to find information and accomplish tasks.
Efficiency- A user's ability to quickly accomplish tasks with ease and without frustration.
Satisfaction- How much a user enjoys using the website.
Error frequency and severity- How often do users make errors while using the system, how serious are these errors, and how do users recover from the errors?
There are two types of usability metrics that can be captured during a usability test. These metrics include:
Performance data- Based on measurements of user's actions, such as time of task; number of errors; recovery from errors; success or failure at task completion; use of help; documentation and r embedded assistance
Preference data- Based on users' responses to questions on post-task and post-test questionnaires. These responses provide quantitative data when they can be measured, using participants' ratings on tasks.