Summary
: How to define usability ? How, when, and where to improve it ? Why should you
care ? Overview defines key usability concepts and answers 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 :
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 ?
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 and together determine whether something is
useful : 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.
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
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 (yielding an improvement score of
2.6) 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 emphasize 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 KPI (key performance
indicator) 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 ecommerce 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 : Before starting the new design, test the old
design to identify the good parts that you should keep or emphasize, and the
bad parts that give users trouble. Unless you're working on an intranet, test
your competitors' designs to get cheap data on a range of alternative interfaces
that have similar features to your own. (If you work on an intranet, read the
intranet design annual to learn from other designs.) 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. The less time you invest in these design
ideas the better, because you'll need to change them all based on the test
results. Refine the design ideas that test best through multiple iterations,
gradually moving from low-fidelity prototyping to high-fidelity representations
that run on the computer. Test each iteration.
Inspect
the design relative to established usability guidelines whether from your own
earlier studies or published research. Once you decide on and implement the final
design, test it again. Subtle usability problems always creep in during
implementation. Don't defer user testing until you have a fully implemented
design. If you do, it will be impossible to fix the vast majority of the
critical usability problems that the test uncovers. Many of these problems are
likely to be structural, and fixing them would require major rearchitecting. The
only way to a high-quality user experience is to start user testing early in
the design process and to keep testing every step of the way.
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.
By
Jakob Nielsen on January 3, 2012
https://www.nngroup.com/
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