How to find the right sample size
If you want to launch a usability test, you need to decide how many testers you need. To help you decide, here's a little guide on how to choose the right number of testers.
Basically, there are three guidelines:
- The larger the sample, the more reliable and better the test result.
- The smaller the sample, the lower your effort.
- The more frequently you test, the fewer testers you need for each test.
To help you decide, we have compiled a few facts about the different sample sizes:
- High accuracy
- With at least 20 testers, it is possible to derive reliable quantitative statements.
- Also suitable for determining tendencies in subjective opinions (e.g. you are currently working on a redesign and want to find out which design variant is more appealing to your target group).
Expert tip: Our customers sometimes use even more test persons to convince their stakeholders of changes and to substantiate the results with quantitative statements.
- Best price-performance ratio
- With 10 or more testers, it is easy to prioritize the main results by frequency of occurrence. The risk of relying on subjective individual opinions is significantly lower than with smaller samples.
- For small budgets
- With at least 7 testers, the risk of relying solely on random individual opinions is reduced.
- Starting at 7 test subjects, the Net Promoter Score (NPS) is collected for unmoderated tests.
- 3-5 testers can be enough to get some good insights and a rough impression - especially with moderated tests that allow for follow-up questions and explanations.
- However, the results are not yet suitable for making final product decisions or prioritizing optimizations. They merely serve to capture individual opinions.
- Our trial offer for unmoderated tests.
- For a first insight into how the site is perceived and operated
- Due to the small sample, however, the 2 tester package is not a valid basis for optimization.
All this information is to be understood per device and use case.
Do you want to test your website on both desktop and smartphone, and do you want to be able to prioritize the results? Then you should opt for at least 10 desktop and 10 smartphone testers.
Of course, you can also choose other sample sizes. In our booking form you are completey free in choosing your sample size
If you have further questions about the topic, just contact us. We are happy to help you!
By the way: Only at your explicit request or in agreement with you, we will invite users who have already tested for you. Otherwise, only users who have not yet tested for you will participate.