The goal of usability testing is to identify any usability problems, collect quantitative data on participants’ performance (e.g., time on task, error rates), as well as determine user satisfaction with the website.
Let’s say it simplier, if a website is difficult to navigate or doesn’t clearly articulate a purpose, users will leave. Making it so they don’t leave, makes testing websites a necessary task.
Usability testing includes the following five components:
- Learnability: How easy is it for users to accomplish basic tasks the first time they encounter the design?
- Efficiency: How fast can experienced users accomplish tasks?
- Memorability: When users return to the design after a period of not using it, does the user remember enough to use it effectively the next time, or does the user have to start over again learning everything?
- Errors: How many errors do users make, how severe are these errors and how easily can they recover from the errors?
- Satisfaction: How much does the user like using the system?
Usability plays a role in each stage of the design process. The resulting need for multiple studies is one reason I recommend making individual studies fast and cheap.