Usability 101: Introduction to Usability

5 quality components:
Learnability: How easy is it for users to accomplish basic tasks the first time they encounter the design?
Efficiency: Once users have learned the design, how quickly can they perform tasks?
Memorability: When users return to the design after a period of not using it, how easily can they reestablish proficiency?
Errors: How many errors do users make, how severe are these errors, and how easily can they recover from the errors?
Satisfaction: How pleasant is it to use the design?

Another key quality attribute is utility. Utility refers to the design's functionality: Does it do what users need?

Usability and utility are equally important and together determine whether something is useful
Definition of Utility = whether it provides the features you need.
Definition of Usability = how easy & pleasant these features are to use.
Definition of Useful = usability + utility.

Why usability is important

Over 80% of people visit our website for work.

They are not browsing; they want to complete a task.

They don’t have time; they have deadlines.

On the Web, usability is a necessary condition for survival.
If a website is difficult to use, people leave.
If the homepage fails to clearly state what a company offers and what users can do on the site, people leave.
If users get lost on a website, they leave.
If a website's information is hard to read or doesn't answer users' key questions, they leave.