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How many customer discovery interviews: what four sources say

Table of four sources on how many customer discovery interviews you need, from saturation by 12 interviews to 20 to 30 to surface most customer needs.
Start with five or six, then keep going until new conversations stop adding themes Source: Griffin and Hauser (1993), Guest et al., PMC saturation research, Cindy Alvarez
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A table of four sources on sample size for customer discovery interviews: Griffin and Hauser (1993) on surfacing 90 to 95% of needs in 20 to 30 interviews, Guest et al. on saturation by 12, research on thematic saturation between interviews 9 and 17, and Cindy Alvarez on a weekly pace of 10 to 15. Use it to set a starting target, then let saturation decide when you stop.

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What's in this reference table

SourceRecommendation
Griffin and Hauser, Marketing Science (1993)20 to 30 interviews to surface 90 to 95% of customer needs
Guest et al., qualitative research methodsSaturation commonly reached by 12 interviews
PMC thematic saturation researchFull saturation typically between interviews 9 and 17
Cindy Alvarez, Lean Customer Development10 to 15 interviews per week during active discovery

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