Editor’s note: Brad Kates is senior consultant at Opinion Dynamics Corp., Cambridge, Mass.

 Market researchers have several methods at their disposal. They have quantitative surveys to get data on specific factors in the marketplace. They have focus groups to help them gain an understanding of key market issues and to help construct more quantitative surveys. And, of course, they have depth interviews. But when should researchers choose the depth interview as their preferred research method? Why should they choose it? And when is it most feasible to conduct such interviews? After all, depth interviews can be a high-cost proposition if they are used improperly.

We have conducted a variety of projects that have involved depth interviewing. Typically, these projects can be placed into one of three different categories:

1. Depth interviews that seek to gain insights from hard-to-reach groups. These help in the development of appropriate quantitative survey instruments, such as telephone or mail surveys.

2. Depth interviews that are the sole research method used.

3. Depth interviews that are used to gather customized information on a subject without being biased by the group dynamic that often occurs in a focus group setting.

Case 1: Hard-to-reach respondents

We recently worked on a business-to-business project in which we helped an energy provider collect information from owners of small commercial buildings regarding their use of lighting. Small commercial building owners are a difficult group to get into a focus group setting. They are typically busy, not prone to meeting with others, and not, in this case, conveniently located (the target group of decision-makers was a cross section of business owners throughout New York state). After meeting with our client, we weren’t sure which questions to ask of this constituency, but we knew they were large market players in the decision-making process for lighting. We decided to conduct depth interviews with small commercial building owners, in which we asked some general questions regarding how they purchase lighting for their facilities. (For example: What barriers exist to purchasing lighting? What selling points do they look for when purchasing lighting? And, what emphasis do their tenants place on installing appropriate lighting?) After gleaning this information, we used it to develop a tangible, targeted quantitative survey to gain statistically representative results that we could report to our client.

In this case, we used the depth interviews to provide background information to support the development of a quantitative survey instrument. The results of the depth interviews will rarely be the data we will analyze to provide recommendations to our client - the purpose is to support the development of an appropriate and targeted quantitative survey instrument.

Case 2: Sole research method

Suppose that you need to gather information from architects in New York State. You are looking not just for any architects, but only architects that specialize in -- and have acute knowledge of - lighting design issues in small commercial buildings. How will you find these people and get this information? Developing an appropriate sampling method will be difficult, if not impossible, because these specific lighting-design-knowledgeable architects do not belong to an exclusive organization, or have their own SIC code. Trying to interview large quantities of these people would be both costly and time-consuming. Conducting a focus group would be nearly impossible because the architects are not centrally located, and they are competing with one another - they will not be open to sharing information freely with their competitors. The best method for obtaining information from this type of group is to conduct depth interviews with key market players.

Depth interviews can delve into important subjects, provide background data on the marketplace, and ensure that researchers speak with the appropriate experts. Depth interviews are also an excellent way to examine corporate buying center behavior within organizations. At the end of the interviewing process, researchers will have key information regarding the current state of the industry, future trends in the industry, and other market actors with whom they might wish to speak.

Of course, by using the depth interview as the sole research method, researchers cannot claim statistical significance in their findings. However, they will be able to better understand the marketplace and make general decisions based on the interviews. Findings can, however, be projectable to a population if, say, six of 10 people have been interviewed. For example, in the case of a project that we recently conducted, we interviewed 200 respondents out of a census of 260 market members. In this case, we were able to project the findings of our study to the entire group of 260.

Case 3: Avoiding group dynamics

Let’s take the case of the rollout of a new product. As part of the product testing, it is ideal for each respondent to touch, smell, and generally “kick the tires” and comment on their likes and dislikes. Conducting focus groups may be tempting. However, allowing a group of 10 people to look and comment on the product at the same time may skew your results to the first person’s comments on the product, particularly if respondents are not passionate about the product in the first place. Depth interviewing enables researchers to talk to respondents one-on-one, eliminating the chance for respondents to be influenced by others as might occur in a group setting.

Conducting depth interviews

While it is important to understand which situations are best suited to depth interviewing, it is also important to think about how to conduct depth interviews.

Researchers can conduct depth interviews either in-person or via telephone. In-person interviews work well for testing new products that people need to see, when respondents are located reasonably close to each other geographically, and when respondents are being interviewed while working. In-person interviews can be conducted at the respondents’ homes, their places of business, or at a central location. For example, we once conducted depth interviews in a limousine near a restaurant to test potential menu items among customers of that restaurant. Telephone interviews work well when interviewing busy executives, respondents from geographically dispersed areas, and when interviewing people for their knowledge (not for their reactions to a new product or service). We used telephone depth interviews for the architect example listed above.

For both telephone and in-person interviews, using a tape recorder is extremely useful. Tape-recording the interviews is especially useful when conducting depth interviews that are functioning as the sole research method (as in Case 2 above) because recording facilitates transcription of verbatim accounts of the interviews that researchers can use to interpret results. It also allows for capturing exact quotes from the conversations, something that makes any client report more impressive and factual.

Another important element to consider when using depth interviews is who should conduct the interviews. We have found that a variety of staff members could be appropriate depending on the level of knowledge that the interviewer needs.

A higher-level staff person should conduct the interviewing if:

  • the client is the one being interviewed;
  • the subject is very technical and lots of jargon is involved;
  • it would encourage the respondent to want to participate.

A lower-level staff person should conduct the interviewing if:

  • the subject is not technical;
  • the budget is a concern;
  • the topic is one with which the interviewer is familiar and comfortable.

Incentives

A final issue of concern is how much of an incentive, if any, to offer a respondent. We have offered respondents cooperation fees (“co-ops”) ranging from nothing to a $10 gift certificate to more than $100. In situations where we are interviewing executives of organizations, we will often make a contribution to a charity of their choice if they agree to be interviewed. In some cases, high-level executives and other respondents that we interview while they are on the job are not allowed to take any form of co-op. It is important to know your desired sample group in order to make a decision about how much of a co-op to provide. Typically, if you are scheduling time to meet with these people either on the phone or in person, a co-op is appropriate. In cases where you are not formally setting up an appointment to speak with your respondents, the co-op can be lower.

Important place

While depth interviews do not allow for generalizations about a population - since most depth interview samples are not statistically randomized and sample sizes are not large enough - they do have an important place in market research. They allow researchers to more deeply explore issues and gain greater understanding in a less structured format than a quantitative survey provides.