It's important to plan how many participants you need to recruit to meet your research goals with reliable results.
Tree testing & first-click testing
For both tree tests and first-click tests, 50 - 100 participants per task will give you trustworthy data (the more the better).
From what we've seen, the trends in participant responses should start to come clear with around 50 participants.
The more participants you recruit from this point, the more confident you can be that the data is representative of your users.
Keep in mind that 50+ completed tasks is ideal — if you get fewer than 50 completed tasks, you'll still get plenty of actionable insights when you dig into the results, especially when looking at participant paths in detail.
Card sorting
For card sorting, we recommend aiming for 30 - 50 participants.
Running an open card sort is a generative exercise: the results give you lots of ideas of how you could label and organize your website content.
The more participants you receive, the higher the potential for complex analysis. Narrowing down the most effective structure from 30 different suggested categorizations will probably be an easier task than from 200 different suggestions!
If your goal is to gather as much data as possible, then don't be afraid to recruit 50+ participants!
Surveys & qualitative research
The sky's the limit! Surveys and qualitative research are research methods with a wide range of use cases. The sample size for surveys can range from a few participants to several thousand participants. For general surveys seeking broad insights, larger sample sizes help to ensure statistical reliability and generalizability.
Qualitative Research: In qualitative research, such as in-depth interviews or focus groups, the emphasis is on gathering detailed insights rather than achieving statistical significance. Here’s what to keep in mind:
Smaller Sample Sizes: Typically, 15-30 participants are adequate for qualitative research, as each session can generate substantial data that provides insights into participant behavior, motivations, and pain points.
Diversity in responses: Including a diverse range of participants ensures a more holistic understanding of different perspectives.
Please note, the number of participants that you can receive in a study is capped at 20,000. If you reach 20,000 participants, your study will be automatically closed.
Prototype testing
The recommended number of participants for prototype testing is 20 or more. Here are a few suggested guidelines:
Initial Usability Feedback: With 20 or more participants, you can start to identify major usability issues. This sample size is generally sufficient to uncover common user challenges and validate design decisions.
Iterative Testing Benefits: If significant changes are made to the prototype after the first round, an additional round of testing with 10-15 new participants can provide validation for the updated design.
Complex Prototypes: For more complex products with numerous interactions, a larger sample size can provide more comprehensive feedback and help identify edge cases.
How to choose
Our recommendations are based on the most common use-cases that we see. However, your project may have its own specific needs!
You may want to base your participant numbers on your own calculations. The number of participants you need for statistical significance can depend on the size of the population you want to survey, the margin of error, and confidence level you are comfortable with.
For example, if you want to test the 500 users on your mailing list, and will accept a margin of error of 10% and a confidence level of 95%, then you will need 81 people to complete your tasks.