The Design Psychologist | Psychology for UX, Product, Service, Instructional, Interior, and Game Designers

The Why Behind Sample Size: How Many People Do You Really Need to Test With?

Jun 30, 2025 · 25 min · Season 1 · Episode 9 · 18.1 MB
0:00-25:01

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How many participants do you need to test in order to make valid research claims? In this episode, we dive deep into the science and psychology behind sample sizes in user testing. Whether you're working with five users or five hundred, the number you choose can shape the story your research tells—and how credible your findings appear to stakeholders.

  • Why sample size is one of the most misunderstood elements in product research
  • The psychological impact of “too few” vs. “just enough” users in high-stakes design reviews
  • Whether the popular idea that "you only need to test five users" is a myth or a useful research guideline
  • How to determine the right number of participants based on your research goals

By the end of this episode, you’ll have a clearer, more confident approach to choosing sample sizes. This will help you create better, more intuitive, and scientifically sound designs.

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