In-depth interviews (IDIs) with customers and experts

Questions this report answers

Why do customers choose us, switch to a rival or cancel, in their own account of events?
What job is the customer hiring our product to do, and what else competes for that job?
What happened, step by step, between noticing a need and buying?
How do specialists see the market's direction and its constraints?
Which moments in our service frustrate users most?
Which hypotheses should a quantitative study test next?

When you need it

IDIs are the method of choice when decisions are personal, complex or sensitive. Typical briefs include understanding why subscribers cancel, reconstructing how a family chose a mortgage or a care home, interviewing doctors, engineers or buyers whose time is scarce, and collecting expert views for a market-entry or investment case. They also suit people who are hard to gather in one place, such as senior managers, rural residents or users of a niche product, because each conversation is scheduled individually, by video, phone or in person, at a time that suits the respondent.

Compared with focus groups, interviews trade group interaction for depth and candour: one respondent can tell a complete decision story, including the awkward parts, without being swayed by others. Compared with a survey, they explain causes but cannot measure how common those causes are, so findings are directional rather than statistically projectable.

Choose another method when the priority is to quantify an issue you already understand, when you want participants to build on each other's ideas, or when observing behaviour, through usability testing or analytics, would answer the question more directly.

Sample table of contents

Executive summary
key findings and what they mean for you
Research design
sample structure, recruitment, format and length
Respondent profile
who was interviewed, by segment, anonymised
Decision stories
typical paths from trigger to choice
Jobs to be done
functional, emotional and social goals behind the purchase
Forces of change
what pushes, pulls and holds customers back
Pain points
where the experience breaks down, and why
Expert perspectives
outlook, constraints and opportunities, where experts are included
Segment differences
how patterns vary by respondent type
Implications
recommended actions and hypotheses to measure next

Methodology and sources

Sample and saturation

IDI samples are purposive: respondents are selected to cover the segments and situations that matter, not to mirror the population statistically. We plan per segment and monitor saturation, the point at which new interviews stop producing new themes. A homogeneous group reaches it sooner; heterogeneous or multi-country samples need more conversations. An interim review after the first batch shows whether to continue or rebalance.

Interview approaches

A semi-structured guide sets topics and probes but leaves room to follow the respondent. For churn and purchase decisions we use jobs-to-be-done switch interviews, which rebuild the timeline from first thought to final decision and capture the forces pushing towards and away from change. Expert interviews use a shorter, focused guide and are usually led by a senior researcher who knows the sector. Where context matters, interviews take place at home, at work or during a shopping trip.

Analysis

Interviews are recorded with consent and transcribed. Each transcript is coded against a framework that combines planned themes with those emerging from the data. We then compare cases across segments, map recurring decision patterns and check whether each insight is supported by several respondents or rests on a single vivid story.

What you receive

Interview guide and screener for your approval
Recordings and full transcripts, translated where needed
Interim findings after the first wave of interviews
Final report with decision maps, themes and anonymised quotes
Persona or job-story summaries for product and marketing teams
Workshop to turn findings into actions and survey hypotheses

How the project runs

Briefing, sample design and screener — 2–4 days
Recruitment and scheduling — 1–2 weeks
Interview guide and pilot interview — 2–3 days, alongside recruitment
Fieldwork with interim review — 1–3 weeks
Transcription, coding and analysis — 1–2 weeks
Report and workshop — 3–5 days

Hypothetical example for illustration

Worked example

Example: an Irish meal-kit subscription service sees many customers cancel after their third or fourth delivery. Exit surveys mostly say "too expensive", yet discounts have not reduced cancellations.

The study combines 18 jobs-to-be-done interviews with recently cancelled customers in Ireland and the UK and six with long-standing subscribers, all by video and about an hour long. Each cancellation is reconstructed from the moment the customer first thought about stopping.

A different picture emerges. Most cancellers had no objection to the price as such; they stopped because unused kits piled up in weeks when plans changed, which made every box feel like waste. The trigger was usually a busy week or a holiday, and "too expensive" was simply the quickest option on the exit form. Long-standing subscribers routinely skipped weeks, while many cancellers did not know skipping was possible.

The company makes the skip function prominent in its app, sends a reminder before school holidays and adds a pause option to the cancellation page. A follow-up survey will size the effect across the customer base.

Common mistakes and how to avoid them

Asking people to predict their behaviour. Respondents are poor forecasters of their own actions; ask about specific past events instead.
Talking more than listening. Leading or closed questions produce agreement, not insight; probe with "what happened next?" and "why did that matter?".
Fixing the number of interviews regardless of saturation. Review after each batch and rebalance thin segments.
Presenting quotes as proof. A vivid quote illustrates a theme but does not show how common it is; that takes a survey.
Interviewing only happy customers. Lapsed customers, rejecters and competitors' users explain more about the limits to growth.

Who it suits

Suitable for	Why
Subscription and digital services	Explain churn and switching beyond exit-survey tick boxes
Financial, health and other sensitive categories	People speak more openly one to one
Teams mapping the customer journey	Reconstruct real decision paths step by step
B2B firms and investors	Buyer and expert interviews inform strategy; see B2B research
Product and UX research teams	Context and motives behind behaviour seen in analytics

Frequently asked questions

How many in-depth interviews are enough?

It depends on how many segments you need to understand and how different they are. Plan per segment and watch for saturation, when new interviews stop adding new themes. A narrow, homogeneous audience needs fewer conversations than a study spanning several countries or customer types; interim reviews tell you when to stop.

How long does an IDI project take?

Three to six weeks is typical. Recruiting busy professionals or rare customer types can take longer than the interviews themselves. Video interviews are quicker to schedule than in-person or in-home visits, and an interim review during fieldwork prevents surprises at the end.

What affects the cost of in-depth interviews?

The number of interviews, how hard and how senior the respondents are, interview length, any in-person or in-home visits, languages and translation, and the depth of analysis. Expert interviews generally need more recruitment effort than consumer ones. Request a proposal describing who you need to hear from.

Should we use interviews or a survey?

Use interviews to discover why and how, and a survey to measure how many. Many projects do both: interviews first to identify reasons and vocabulary, then a survey to quantify them. If you already know the options and need numbers, start with a survey and size it with our sample size calculator.

Can you interview our customers on our behalf?

Yes. Provided you have a lawful basis to share your customer list, we contact customers under our own name, tell them where their details came from and report anonymised findings unless a respondent explicitly agrees otherwise. That independence usually draws more candid feedback than interviews run by your own staff.

How are interview recordings and personal data protected?

Respondents consent to recording and to the stated use of their data. Recordings are stored securely, access is limited to the project team and files are deleted after the agreed retention period. Quotes are anonymised, and the work follows GDPR and the ICC/ESOMAR International Code.

Sources

Updated: 5 Nov 2026

In-depth interviews: one-to-one conversations that explain why people decide as they do