An Overview of One-on-One Interviews

General format: The format for interviews tends to be very flexible: the length, the location, and the degree of structure and formality can vary enormously depending on the circumstances of the interviewers and the interviewees.
In person or by phone: Interviews are typically conducted in person, especially if you want a reaction to specific materials. However, you may be able to do interviews over the telephone if you're gathering impressions and ideas from key informants (especially if you already know them).
Multiple rounds: If you are using interviews as part of your developmental testing, you will need to do multiple rounds so that you can test the changes you made as a result of the initial feedback. This iterative process may not be realistic for all sponsors or all projects, but you should plan on at least two rounds if at all possible.
Costs: The expenses associated with interviewing are primarily driven by three factors:

The interviewer's time to develop protocols/questions, prepare materials you're testing, recruit participants, conduct interviews, and write up results.
Participants' honoraria to compensate them for their time (usually $25 to $50 each; however, employees recruited for this purpose often are not paid when interviews are done on company time).
The facility fee (a common but avoidable expense if you or a partner can donate appropriate space).

Number of participants: The ideal number of interviewees depends on what stage of the project you're in, what kind of project you're doing, and the kinds of respondents you're dealing with. The typical number ranges from 5 to 15 people. Even a fairly small number of people can provide a wealth of useful information, especially if you conduct several rounds of testing. Generally speaking, once you can detect a definite pattern in the responses, you probably know enough to make changes for the next round.
Time required: Each interview typically takes anywhere from 20 minutes to an hour (sometimes more, but try not to exceed an hour). While you can conduct interviews in as little as two weeks or so, it's ideal to plan for a four to eight-week process. This is the time needed to:

Staffing: Experts suggest that interviewers work in pairs so that one person can ask questions while the other record the responses in as much detail as possible. Select to access an example of an interview guide, Concurrent Cognitive Interview Protocol, (PDF file, 66 KB; HTML).
© Copyright 1998. Research Triangle Institute. All Rights Reserved. Used with Permission.
Preparing the interviewee: The first thing you should do is to tell the person about the purpose of the interview and the process you will use to interview them. Make sure they understand that you want them to react honestly and critically because their feedback will help you improve the materials they're seeing. In that context, explain why you are taking notes and/or taping the conversation, and reassure them that their responses are confidential.