To conduct usability testing, you don’t need a large number of participants. The most optimal group size is a batch of five individuals for each design variation. Testing with five people is the ideal number for a usability test. It’s the perfect size to cover various aspects of the layout or product design without falling into the routine of repetitive responses. Jakob Nielsen, one of the most renowned and authoritative researchers in the field of usability and user experience, provides more detailed insights into this. He is also one of the founders of an American computer user interface and user experience consulting firm, the Nielsen Norman Group, which advocates for evidence-based user experience (UX) research, training, and consulting.
Usability Testing with 5 Users: Design Process
During usability testing, Jakob Nielsen recommends testing with a small group of participants, typically around five. This approach is advantageous because, during the initial test with the first user, everything observed is fresh and intriguing. This is the very purpose of usability testing—to understand how customers interact with our design.
However, as subsequent users are tested, some observations may overlap with what was seen with the first user. While people exhibit individual behaviors, there will still be some commonalities. Testing with the third person may reveal similarities with the first and second users, and as you progress, the novelty diminishes. By the time you test the fourth and fifth users, you’ll likely encounter more repetition and fewer novel insights. Testing with more than five users can often yield diminishing returns.
The key lies in utilizing the insights gathered from these initial tests to enhance the user interface design. Create a new iteration, test it with another group of five users, and repeat this process as long as your budget allows. For instance, if your budget permits testing with 20 users for a design project, it’s often more beneficial to divide them into four tests, each with a different design iteration, tested by five users. This approach results in more significant design improvements, which is the primary goal of usability testing.
It’s important to note that some research types may require more users, such as quantitative usability studies where statistical significance demands a larger sample size. However, for standard usability testing aimed at improving design quality, less can often be more. The number of users needed may also depend on your ability to extract insights and your team’s efficiency in implementing design recommendations. In some cases, two users may suffice, while in others, more participants may be required. On average, the recommendation remains to test with five users.
Usability Testing with 5 Users: Information Foraging
When conducting usability testing, our goal is to uncover usability problems and identify design flaws that require improvement. This process bears a resemblance to the information foraging theory, which suggests that the way humans seek information is akin to how wild animals hunt for food in nature.
To illustrate, imagine a forest teeming with rabbits and divided into two areas: Patch A and Patch B. In Patch A, there are four rabbits, while in Patch B, there are two. Where should the fox focus its hunt?
Clearly, the fox would choose Patch A, where the game is more abundant. Now, let’s consider a scenario where the fox has caught and eaten three unfortunate rabbits in Patch A, leaving only one, while Patch B still has two. Should the fox persist in hunting the last rabbit in Patch A or migrate to the richer hunting grounds in Patch B?
The logical choice is for the fox to venture to the richer hunting grounds, a behavior observed by biologists in their studies. Similarly, in our usability studies, we should not exhaustively hunt down every usability problem in the initial version of our design. Instead, it’s prudent to pause, typically after testing with five users, and acknowledge that we’ve uncovered a substantial number of issues. It’s then time to transition to “richer hunting grounds,” represented by version two of our design.
Version two promises a wealth of new discoveries because, ideally, we’ve already identified and addressed many of the major obstacles in version one. This allows users to engage more deeply with the user interface, resulting in the discovery of fresh, intriguing usability problems. Additionally, it’s worth noting that not every attempted fix in version one may truly resolve an issue; sometimes, it introduces new usability problems. These can be unearthed during testing in version two.
Finally, any usability problem from version one that remained undiscovered and unresolved will persist in version two, awaiting discovery. This situation differs from the fox analogy because usability problems can persist between design iterations. Therefore, it’s advisable to follow the principle of not hunting every usability problem to extinction in one iteration but to explore other avenues and allocate resources for better outcomes.
Where’s the best place to find users for usability testing?
Additionally, it depends on your budget. You can use people from other departments who weren’t involved in product creation, but it’s even better to involve representatives of your target audience. This can provide higher-quality data with an understanding of your audience’s context. To recruit users from your product, send an email offering them participation in testing and assistance to the product. However, considering declining email open rates, it’s better to try sending offers directly on your website or in your product using our survey feature. Users will see a pop-up, and if they’re interested in helping you, they’ll leave their contact information or register for a call with you if you provide a link to your Calendly.
