depth interview
noun[C]
MARKETINGukus(alsoin-depth interview)anoccasionwhen someone isaskeddetailedquestions, forexample, about theproductsorservicesthat theybuyor would like tobuy:
Depthinterviewsare ausefultypeofqualitativemarketresearch, and are often to bepreferredtofocusgroups.
depth interviewing
noun[U](alsoin-depth interviewing)
Depthinterviewingoftenrequiresrepeatedsessionswith theinterviewee.