In this guide, we'll explore the ideal number of participants to interview in two different scenarios:
Conducting usability testing
User interviews for market research
Usability testing vs user interviews
Usability testing is a method of testing the functionality of a website, app, or other digital product by observing real users as they attempt to complete tasks on it.
- The goal of usability testing is to uncover usability issues in your prototype, website, or app.
User interviews are discussions with participants that match a certain criteria, allowing researchers to ask questions and learn more about their research topic.
- The goal is to understand the market and customer needs in more depth.
How many usability tests should you run?
It's widely accepted that running five usability tests will uncover most of your usability issues for the least amount of time and money invested.
As Jakob Nielsen, former VP of research at Apple Computer, explains: “With five users, you almost always get close to user testing's maximum benefit-cost ratio.”
This means you'll uncover the most important usability findings from five users. After testing with five users, we recommend making adjustments to your prototype or design, and then starting a new batch of interviews.
How many user interviews should you run?
User interviews are slightly different from usability testing, and there are many factors to consider when deciding on an ideal number of interviews to run.
Starting with five users is still a good choice, but be prepared to conduct more interviews, potentially as many as eight to fifteen, depending on the size of the market you're serving, the complexity of your product, and more.
In usability testing, there will be a finite number of usability issues in your prototype, which is why five is generally enough interviews to uncover them.
However, with user interviews, there is always more to learn about the target audience, their pain points, the jobs they need to do, and more.
This is especially true if your product or service will target multiple personas, so don't be surprised if you discover a need for more than fifteen user interviews. The insights you gather will be worth it.