Introduction to Usability
How to define usability? How, when, and where can you improve it? Why should you care? This overview answers these basic questions.
This is the article to give to your boss or anyone else who doesn’t have much time, but needs to know the basic usability facts.
What — Definition of Usability
Usability is a quality attribute that assesses how easy user interfaces are to use. The word “usability” also refers to methods for improving ease-of-use during the design process.
Usability is defined by 5 quality components:
There are many other important quality attributes. A key one is utility, which refers to the design’s functionality: Does it do what users need? Usability and utility are equally important: It matters little that something is easy if it’s not what you want. It’s also no good if the system can hypothetically do what you want, but you can’t make it happen because the user interface is too difficult. To study a design’s utility, you can use the same user research methods that improve usability.
Why Usability is Important
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.
Note a pattern here? 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; leaving is the first line of defense when users encounter a difficulty.
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. Time users waste being lost on your intranet or pondering difficult instructions is money you waste by paying them to be at work without getting work done.
Current best practices call for spending about 10% of a design project’s budget on usability. On average, this will more than double a website’s desired quality metrics and slightly less than double an intranet’s quality metrics. For software and physical products, the improvements are typically smaller — but still substantial — when you emphasise usability in the design process.
For internal design projects, think of doubling usability as cutting training budgets in half and doubling the number of transactions employees perform per hour. For external designs, think of doubling sales, doubling the number of registered users or customer leads, or doubling whatever other desired goal motivated your design project.
How to Improve Usability
There are many methods for studying usability, but the most basic and useful is user testing, which has 3 components:
- Get hold of some representative users, such as customers for an e-commerce site or employees for an intranet (in the latter case, they should work outside your department).
- 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.
It’s important to test users individually and let them solve any problems on their own. If you help them or direct their attention to any particular part of the screen, you have contaminated the test results.
To identify a design’s most important usability problems, testing 5 users is typically enough. Rather than run a big, expensive study, it’s a better use of resources to run many small tests and revise the design between each one so you can fix the usability flaws as you identify them. Iterative design is the best way to increase the quality of user experience. The more versions and interface ideas you test with users, the better.
User testing is different from focus groups, which are a poor way of evaluating design usability. Focus groups have a place in market research, but to evaluate interaction designs you must closely observe individual users as they perform tasks with the user interface. Listening to what people say is misleading: you have to watch what they actually do.
When to Work on Usability
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. Here are the main steps:
Where to Test
If you run at least one user study per week, it’s worth building a dedicated usability laboratory. For most companies, however, it’s fine to conduct tests in a conference room or an office — as long as you can close the door to keep out distractions. What matters is that you get hold of real users and sit with them while they use the design. A notepad is the only equipment you need.
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