Marketing Research Methods: Focus Group vs. Depth Interview

When considering marketing research methods, consider this: depth interviews produce as much information as focus groups, and sometimes more.

Here’s why. The depth interview respondent spends more time talking than a focus group respondent.

On average, each focus group respondent only talks for about 9 minutes in a 90 minute focus group. Compare this to a 25-minute depth interview.

Here’s the proof.

Assume the following, which is typical:

  • A focus group has 8 people and lasts 90 minutes.
  • An depth interview lasts 25 minutes.
  • The moderator speaks 20% of the time and respondents speak 80%.

In this example, each focus group respondent has 9 minutes to speak if everyone speaks equally.

90 minutes x 80% divided by 8 respondents = 9 minutes talk time each.

In the example, the depth interview respondent speaks for 20 minutes.

25 minutes x 80% divided by 1 respondent = 20 minutes talk time

And look what happens when you add more respondents to a focus group. Average respondent talk time goes down. 10 focus group respondents cut average talk time to about 7 minutes a respondent.

The Case for Depth Interviews

With more talk from a respondent, you'll likely get more depth about topics from a respondent. And if you speak to several respondents with diverse experiences, you'll likely get breadth.

And telephone depth interviews are less expensive than focus groups because they do not incur facility rentals and travel costs as focus groups do. If you are on tight research budget, use telephone depth interviews.

Also, telephone depth interviews are effective for interviewing people who have limited time to attend focus groups: experts, senior executives, professionals, and magazine editors.

Depth interviews are effective when talking about sensitive subjects people would rather not talk about in front of groups of people.

And depth interviews are good for usability studies.

Most managers can conduct depth interviews with the right questions. Interviewing one person at a time is easier than moderating several people at a time.

So there is a strong case for depth interviews.

The Case for Focus Groups

On the other hand, focus groups are efficient if you want to interview groups of people at a short time period. You can conduct 8 groups in 4 days, for example.

In theory, focus groups produce dynamic discussion. One person’s statement spawns others to talk. A skilled moderator conducts dynamic discovery and exploration of topics.

In face-to-face focus groups, managers can watch and listen to respondents. It's a chance for office bound managers to get out and hear and see real customers and prospects, and gain new perspective and insight. Hearing and seeing customers or prospects is powerful way for managers to connect to the marketplace.


Combining depth interviews and focus groups uses the strength of each marketing research method.

For example, you use depth interviews to interview subject matter experts, industry executives, or channel personnel, in early stage research. They provide topic discover, breadth, and depth.

Then use focus groups with targeted user segments for concept testing and market tests. They provide reactions to ads, brands, products, or services.

Depth interviews and focus groups are effective marketing research methods. They are similar but different tools. Use each method for the right application and budget.

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