An interview conducted with two participants at once, who may know each other, or may be recruited as strangers. If known to each other, they are sometimes referred to as a friendship pair, this is used especially for children or young respondents (who gain security from the presence of a friend).

Another common application is in research concerning decisions made jointly by couples, such as buying a car or choosing a holiday, or for interviews with mothers and children. If not known to each other, participants may be recruited as having similar behaviour and interests, or as a conflict pair. The latter is designed to dramatise differences between, for example loyal users of two different brands.

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A form of depth interview involving three participants, who may or may not know each other. It offers some of the advantages of group discussions, but also some of those of depth interviews. As is the case for paired depths, triad participants may be recruited to form a homogenous group, or alternatively to set up a degree of conflict (where each member takes a particular view on an issue, or uses a quite different brand of the same product, for example).

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