How To Plan & Conduct a Qualitative Depth Interview

One of the paradoxes of research is that many people feel confident designing a questionnaire, but are very nervous about how to approach qualitative research. In reality it’s often much easier to do qualitative research than it is to design a good quantitative questionnaire.

In this guide we’ll talk you through the essentials.

You can download a PDF copy of the guide here.

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A qualitative depth interview should look much more like a conversation than an interview. It’s probably best to forget the word “interview” altogether, but if you do want to use that as a starting point think of the kind of interview a journalist would do rather than a series of closed questions.

Depth interviews typically last anywhere from 20 minutes up to an hour and a half, depending on the subject matter, who you’re talking to, and how.

You’ll want to have a discussion guide, which will help you to structure and steer the conversation, but it’s really important you see this as a guide rather than a script. The conversation should be led, to a large extent, by the person that you’re speaking to. As a rule, the less talking you do, the better.


A depth interview is designed to get you as close as possible to understanding how one individual (or occasionally a small group of people) thinks and feels about a topic. In customer research it’s often focused on what matters to customers, what their needs and expectations are, and how they make purchasing decisions.

You should use depth interviews whenever you feel that you need to know more about customers, whether that’s at a general level to understand their lives and the context in which your product or service is used, or when it comes to their needs and attitudes in specific journeys.

If you’re planning a quantitative survey, you should almost always start with some qualitative insight in order to make sure that you ask the right questions in the right way.


You want to talk to a selection of customers which is representative, but not in a statistical sense. Look for a range of different types of customer who are likely to have different perspectives. A good rule of thumb is to ask “who will I learn most from?”

In business to business markets make sure that you include people not just from different sectors, but also different roles across the “decision making unit” (including, for example, end users, influencers, buyers, technical contacts, and decision makers). If you don’t have contact details for everyone you can use a “snowball sampling” approach and ask for introductions to relevant contacts at the end of each interview.


You can do the interview wherever and however is most comfortable for the customer. Traditionally, depth interviews were conducted face to face in customer’s homes or offices (although we’ve done plenty in service stations, cafes, and hotel lobbies!)

Increasingly video depth interviews are becoming an effective alternative, and while you tend not to get quite such good engagement with the customer, they are a good option for most. Telephone interviews can also work, but give you significantly less depth. One thing you miss out on with these methods is the ability to observe the customer’s environment, which can often be a fruitful source of insight in itself as well as prompting questions.


Although depth interviews are normally very loosely structured, that doesn’t mean that you don’t need to do any work beforehand. You’ll need a “discussion guide”, which is essentially a list of topics that you would like to cover. Make sure your questions are open-ended, and think of some ideas for prompts that you might want to use to follow up the initial question. There’s an art to judging these right, so that you encourage the interviewee to open up and talk rather than peppering them with quickfire questions.

The single most important skill of the qualitative researcher is listening.


It’s a mistake for the interviewer to try to take detailed notes during the interview it’s simply not possible to actively listen, respond with intelligent probes, and take good notes all at the same time. It’s a good idea to take very brief notes, which might include key points and questions you want to follow up, but if you need full notes to be taken in the moment you’ll need to bring someone else along with you.

It’s much more common, and easier in most cases, to record the interview. Obviously you’ll need to ask the interviewee’s permission, and be clear how the recording will be used, but this is normally not a problem.

However you recorded the interview, try to make sure that you set aside 5 or 10 minutes after the interview to write down your top level thoughts, takeaways, and reflections. We usually do this in the car outside the customer’s office before we set off. There’s a golden window of opportunity when these thoughts are fresh in your mind, but it’s surprising how quickly they fade!


The single most important skill of the qualitative researcher is listening. We like to think about a “ladder” model, where what you’re trying to do is work downwards from what customers say to what they mean—deeper levels of meaning that reveal more profound drivers, needs, and motivations. Working your way down the ladder requires a well-judged mixture of listening, asking questions in the right way at the right time (often the best probe of all is a second of silence), and interpretation.

If that last one sounds a bit subjective, it’s because it is, but that’s actually a strength rather than a weakness. As long as you are conscious of the potential to introduce bias through your own thoughts and preconceptions, and work to offset that, you can use your ability to interpret what people say, and why, to draw richer insights about customers and their world.


Analysing and writing up qualitative research is notoriously tricky and “black box”, but you’re not trying to publish an academic paper. Start with your raw data (transcripts, notes, potentially photos or other artefacts) and re-read everything.

Then read it again, this time looking to sort things into themes that seem to group together—this can be a long, iterative, back-and-forth process! There’s software that can help, but many people prefer to work with index cards, Post-Its, or mind maps.

Your findings will depend on the purpose of the research, but some important things to look for are: themes; consensus (what’s typical) and variation (what are the exceptions, and why); cause and effect; context. All of this should be summarised as punchily as possible, ideally with diagrams and pictures to bring it to life, and illustrated with a few choice quotes.


During the interview itself, the most important thing to be aware of is to not lead the customer or assume you know what they’re going to say. Similarly, in the analysis, it can be valuable to work with a colleague to make sure that you’re not doing too much interpretation instead of relying on the evidence that’s really there.

On the other hand, it is important that you make those interpretative judgements. Your report should never be just a collection of quotes from customers.


Qualitative research is incredibly important, but underused in many organisations, particularly in B2B markets. Depth interviews are a convenient, powerful, and cost-effective tool that every business should be making use of to get closer to customers and design better propositions and experiences for them.

+ Pros

  • Unparalleled understanding of how customers make decisions, and what matters to them

  • Cost-effective and powerful

  • Engaging and detailed feedback from key customers

- Cons

  • Hard work to analyse and share the insights

  • Not everyone understands the value of qualitative research

  • Not suitable to draw statistical conclusions about all customers

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