Why You Only Need 5 Users for Effective Usability Testing
When you’re considering designing or updating a website or application, the question of usability testing often arises. How many users should you test to get reliable results? Some believe that it takes dozens or even hundreds of users for effective testing. However, Jakob Nielsen, a renowned expert in user experience, proposed a surprising idea in 2000: you only need 5 users. In this article, we will explore why this approach could save you time and money while improving the efficiency of your usability tests.
The Law of Diminishing Returns
Nielsen’s philosophy is based on what he calls the “law of diminishing returns” in usability testing. This law states that the value of collected data decreases as the number of tested users increases. In other words, after testing with only 5 users, you will have already discovered the majority of usability issues.
Why does this work? When you test with a single user, you already gain a significant insight into major issues. The second user may bring some repetitions but also new perspectives. However, as you add more users, you’ll find that identified issues repeat themselves, providing less diverse results.
The Iterative Approach in an Agile Context
Instead of spending significant resources on testing with a large number of users from the outset, Nielsen advocates an iterative approach. This means you can allocate your usability testing budget across multiple sessions with 5 users each.
After the first series of tests with 5 participants, where you discover most issues, you can make improvements to your design. Then, you conduct a second series of tests to assess whether the changes have resolved the problems. This iteration continues until you are satisfied with the user experience.
Quick and Clean Testing in an Agile Setting
Within this iterative approach, you can employ “quick and clean” testing techniques. This involves conducting tests with a small group of users and rapidly iterating on design improvements. The aim is to address usability issues promptly, making your design cleaner and more user-friendly.
Advantages of this Approach
Time and Cost Savings: Testing with a small group of users at a time is more cost-effective than investing in a single massive test.
Early Issue Discovery: You quickly identify major problems from the beginning, allowing you to address them before they become critical.
Continuous Improvement: The iterative approach, with quick and clean testing, enables continuous improvement of your design as you can make adjustments along the way.
Risk Reduction: Iterative testing minimizes risks associated with introducing new problems during design updates.
When to Test with More Users
Of course, there are situations where you will need to test with more than 5 users. This typically occurs when your website or application targets very different user groups. For example, if your product needs to be used by both children and adults, usage behaviors will vary significantly. In such cases, it may be wise to test with more users to ensure adequate coverage.
In Conclusion, Jakob Nielsen’s approach favoring usability tests with only 5 users offers many advantages. It allows for time and cost savings while ensuring early issue discovery. Employing quick and clean testing techniques within an iterative approach helps create user-friendly digital products, significantly improve the user experience, and reduce waste, aligning perfectly with the Lean JX mindset.