The short answer (and consensus among my mentors and colleagues): you only need to interview 5-6 people during user research, because you’ll gain 75% of your findings after speaking to the third user. And things usually taper off after the 5th – 6th user.
Phew, not so bad.
The long answer: it really depends on what you want to do and how much you already know. The more focused and confident you are, the lower the number. The less focused and confident you are, the higher the number.
For example, if you want to improve usability in an already existing experience, then 5-6 is all you need (because we humans are wildly similar when it comes to cognition). If you need to validate market segments before creating personas – you already have a clear sense but need to be sure – then the magic number is closer to 12 per segment (because social and cultural influences also play into it). If everything is still vague and up in the air or you’re just starting out, then you should talk to as many people as possible and fine-tune your definitions along the way. Though from my experience, the number probably won’t be as high as you think for each round.
If you’re feeling overwhelmed, just remember that talking to some is better than talking to none. The real trick is talking to the right ones. More on that later.
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