Meeting, listening to, and observing real users (or potential users) is how to validate and refine hypotheses about your users and your product. For most consumer products, 5-8 interviews is usually about right. For business products, 3-5 interviews per role is a good rule of thumb, with a mix of:
If there is a clear primary persona, extensive research with secondary personas (system admin, for example) is not necessary — 1-2 interviews may be enough.
|Typical Length||About 1 week per 10 interviews (including time to reflect, synthesize, and review the results)|
|Logistics||Research should ideally be in person, one-on-one, and on location in the context where people would use your product.|
|Deliverables||Personas; research summary; updated product vision statement|