Into the usability rabbit hole

Usability design is comparable to the white rabbit that Alice intuitively follows. It serves as an invisible guide, fascinates, fuels anticipation and captivates. Fortunately, no magic wand is needed to create this magic. All it takes is a sophisticated test strategy and a guerrilla unit of three to five usability testers.

We are constantly confronted with digital user interfaces in our everyday lives and at work. Washing machines, car radios, complex controls for machines and, of course, websites and applications - we happily click our way through the digital landscape. At best, without giving it much thought. This intuitive user experience is created by a sophisticated usability design.

In principle, every new digital product should be tested for functionality and intuitive handling by selected test persons from the identified target group. Ideally, these test phases should be started during development with clickable dummies.

But even established websites or apps tend to be overloaded with information or get lost in growing structures. Only through the eyes of your own target group can all relevant problem areas be made visible and - in favour of a positive user experience - eliminated.

Around 30 years ago, when the internet and digital user interfaces were still in their infancy, a study by UX pioneers Jakob Nielsen and Tom Landauer came up with a formula for meaningful usability tests while minimising time and costs. This formula is still relevant today:

N stands for the total number of usability problems of the product at hand and L for the number of problems recognised by a single test person. Probably the most important finding of Landauer and Nielsen is that zero tested users bring zero results. The second most important finding is that the value of L is 31% on average.

Because people generally behave similarly, some of the problems found are duplicated from the second test subject onwards. This reduces the percentage of new findings. The third person will repeat even more of the actions of the first or second test person. Some things will even be the same for all test subjects. The more people you ask about the application, the fewer new findings there will be. Nevertheless, several test subjects should always be consulted, as the results may vary. The statements of a single person are never meaningful enough for a serious test. Depending on the product and the size of the target group, several test phases with at least three to a maximum of five people have proven to be effective.

The first test phase with three to five people can localise almost three quarters of the existing problems in a user interface. But what about the remaining errors? No, ignoring them is not an option. Nevertheless, the errors found should be rectified before the next test phase.

The resulting redesign is tested with three to five new people. These now provide valuable information on whether the problems could be fixed or whether new weaknesses have even arisen. Test phase two also deals with the underlying structures of the product in question. According to the study by Nielsen and Landauer, 15% of the original problems that went unnoticed in test phase one are found here. After reworking the design on the basis of the findings, only 2% of the original problems remain and the redesign enters test round three. This is important in order to find the last initial problems and to check all the changes made for their suitability.

To avoid getting bogged down in a never-ending test story, this is usually the end of the road. The formula for usability success says: three guerrilla test phases with three to five test persons offer an optimal cost-benefit ratio for usability tests.

In the course of the three runs, not only are insights gained into acute usability problems, but also into the behaviour of the target group. The designers involved receive important information about the needs of the users, which can be directly incorporated into troubleshooting. In this way, the ultimate usability is created at several intervals. Isn't that such a win-win?

Usability is a bit like the white rabbit that Alice intuitively follows. However, this white rabbit of the digital world changes course from time to time. For example, whenever large providers introduce an innovation that influences the habits of users. Usability is not a rigid concept, but a constantly changing world of emotions and the resulting actions. The topic of usability should therefore never be ticked off as ‘done’. Only those who have the smooth usability of their application constantly checked by the watchful eye of their own target group in meaningful usability tests can survive on the digital market in the long term.