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Methodology · 4 min read

In-Depth Interviews Sample Size and Sampling Guide for India

How to choose the right sample size and sampling approach for in-depth interviews in India, including quotas, city splits and segment reads.

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Quick answer

The right sample for in-depth interviews depends on how many segments you need to read separately and how precise each reading must be. In India, also plan quotas by city tier, region, age, gender and socio-economic class (NCCS).

At a glance

Guide type
Methodology · 4 minute read
Method covered
In-Depth Interviews
Research family
Qualitative research
Typical timeline
4–6 weeks from guide sign-off to the thematic report
Typical sample
20–30 interviews per audience, stopping when new themes stop appearing
Written for
Analysts sizing the sample · Data leads reviewing a design · Anyone asked “is this enough?”

Key takeaways

  • Plan sample per segment, not just in total
  • Use NCCS for socio-economic quotas in India
  • Weight results to match the population
  • Qualitative samples are about saturation, not statistics

Reader intent

Who this guide is for

Three readers arrive here with different problems. Each should be able to act on this page without reading all of it.

  • Analysts sizing the sample

    How to get from a decision to a defensible in-depth interviews sample, rather than to a round number.

  • Data leads reviewing a design

    Frames, quotas, weighting, and the bases you can and cannot report on.

  • Anyone asked “is this enough?”

    The answer depends on the precision the decision needs. This guide shows how to work that out.

01

Start with segments

Decide which groups you must compare, for example metro versus Tier 2, or users versus non-users. Each needs a robust base.

02

Quotas that matter in India

  • City tier and region
  • NCCS socio-economic classification
  • Age and gender
  • Category usage
  • Language

03

Qualitative sample design

Qualitative studies aim for thematic saturation: the point where new interviews stop revealing new themes. Spread groups or interviews across regions and segments.

04

How Market Research India can help

Market Research India designs and runs in-depth interviews projects across 50 Indian cities and 30 industries. A senior research director leads every study, and our own supervised teams handle the fieldwork. You get clear recommendations, not just data tables.

Share your objective and we will send a scoped, fixed-fee proposal within 24 hours, with a recommended method, sample and timeline.

What goes wrong

Common mistakes in in-depth interviews

Most disappointing in-depth interviews studies fail for reasons that were visible in the design, not in the fieldwork. These are the ones we see most often, and what to do instead.

  • 01

    Questions that carry their own answer

    “What do you dislike about the service?” presumes dislike. Ask what happened last time, then follow the story rather than the hypothesis.

  • 02

    Accepting the first answer

    The first response is a rationalisation. Laddering — asking why that matters, three or four times — is what separates a depth interview from a long survey.

  • 03

    Recruiting everyone from one source

    Twenty-five interviews all sourced from a single customer list describe that list, not the market. Use at least two independent recruitment routes.

  • 04

    Counting mentions as if they were data

    “14 of 25 said” lends a qualitative sample the authority of a survey it has not earned. Report themes and their reasoning, and quantify separately if you need numbers.

  • 05

    Moderator bias nobody checks

    A moderator who already believes the answer nods at agreement and probes only dissent. Brief on the decision rather than the hypothesis, and review the first session before the rest go ahead.

  • 06

    Regional language nuance lost in translation

    Category language in Hindi, Tamil or Marathi rarely survives live translation. Work in the respondent's language and translate the transcript, not the conversation.

Run through this before sign-off

Your checklist before you brief anyone

A working sequence for a in-depth interviews project. Most of it costs nothing, and it saves the two weeks a re-field would take.

  1. 1

    Write the screener before the discussion guide; who you talk to decides more than what you ask.

  2. 2

    Pilot two interviews and rewrite the guide before the rest are scheduled.

  3. 3

    Record and transcribe with explicit consent, and keep the recording in the interview language.

  4. 4

    Ladder every important answer with “and why does that matter to you?” at least twice.

  5. 5

    Code to a shared framework, so two analysts reading one transcript reach the same themes.

  6. 6

    Hold a same-day field debrief, before impressions harden into a story.

  7. 7

    Agree in writing who acts on each finding, and by when, before the debrief ends.

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Answers

Frequently asked questions

The questions buyers ask us most often before they commission in-depth interviews.

What is NCCS?

The New Consumer Classification System, India's standard socio-economic classification based on education and household durables.

Request a proposal

Talk to a in-depth interviews specialist.

From guide to project

Where in-depth interviews actually gets commissioned

If this guide has settled the method, these are the pages worth opening next: the service itself, and the markets where in-depth interviews is most often run for our clients.

Keep exploring

More reading on in-depth interviews

Grouped rather than listed, so you can find the one page you need instead of scanning a wall of links.

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