Jakob Nielsen’s Introduction to Usability

Prepared by Mithat Konar

2011–11–14

Jakob Nielsen’s Introduction to Usability

• Adapted from
  • “Usability 101: Definition and Fundamentals - What, Why, How (Jakob Nielsen’s Alertbox).” useit.com: Jakob Nielsen on Usability and Web Design. http://www.useit.com/alertbox/20030825.html (accessed November 14, 2011).
• For
  • COME 336 :: Interface Design for SW Engineers

What — Definition of Usability

What — Definition of Usability

• Usability: a quality attribute that assesses how easy user interfaces are to use.
• Also refers to methods for improving ease-of-use during the design process.

What — Definition of Usability

• Usability is defined by 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?

What — Definition of Usability

• Utility is another important quality attribute.
  • Refers to the design’s functionality
  • “Does it do what users need?”
• Usability and utility are equally important:
  • Program can do what you want to do but it’s too hard: bad
  • It’s easy to do something that you don’t want to do: bad

Why Usability is Important

Why Usability is Important

• Usability is a necessary condition for survival on the Web.
  • “There’s no such thing as a user reading a website manual or otherwise spending much time trying to figure out an interface. There are plenty of other websites available.”
  • The first law of e-commerce is that if users cannot find the product, they cannot buy it either.
• For intranets, usability is a matter of employee productivity.
• Both apply in various ways to desktop applications.

Why Usability is Important

• Spending about 10% of a Website’s design budget on usability:
  • More than doubles a Website’s desired quality metrics
  • Slightly less than doubles an intranet’s quality metrics.
• Improvements are smaller but still substantial for software and physical products.

How to Improve Usability

How to Improve Usability

• Many methods for studying usability.
• The most basic and useful is user testing.
• Three components of user testing:
  • Identify some representative users
  • Ask the users to perform representative tasks with the design.
  • Observe what the users do, where they succeed, and where they have difficulties with the user interface. Shut up and let the users do the talking.

How to Improve Usability

• Test users individually and let them solve any problems on their own.
  • If you help them, you have contaminated the test results.
• Testing five users is typically enough to identify a design’s biggest problems.
• It’s a better use of resources to run many small tests and revise the design between each one.
• The more versions and interface ideas you test with users, the better.

How to Improve Usability

• User testing is different from focus groups.
  • You must closely observe individual users.
• Listening to what people say is misleading: you have to watch what they actually do.

When to Work on Usability

When to Work on Usability

• Usability plays a role in each stage of the design process.
• Begin user testing early to catch critical usability problems before you’re overcommitted.
• Test every step of the way with fast and cheap studies.

When to Work on Usability

• Main steps:
  • Before starting the new design, test the old design to identify the good and bad parts.
  • Test your competitors’ designs to get cheap data on a range of alternative interfaces that have similar features to your own.
  • Conduct a field study to see how users behave in their natural habitat.
  • Make paper prototypes of one or more new design ideas and test them.
  • Refine the design ideas, moving from low-fidelity prototyping to high-fidelity representations. Test each iteration.
  • Inspect the design relative to established usability guidelines, whether from your own earlier studies or published research.
  • Test final designs as well to make sure nothing creeped in.