Three steps to the perfect sample

Defining the right sample and target population in research can be a real challenge. Imagine having an exciting research question but being unsure who you should actually survey. Too broad or too specific—both can cause problems.

In this article, you’ll learn step by step how to define your sample, which methods are available, and what you should pay attention to. A well-thought-out sampling strategy ensures that your empirical study produces meaningful and scientifically sound results.

Why is choosing the right sample so important?

Every piece of empirical research is based on data—and that data must be collected from the right people. Your results depend largely on whom you survey. An unsuitable sample can distort your entire study or even render it worthless.

“If I ask a question that somehow concerns everyone and the concept is very broad, it may not really tell us anything. And if it’s too narrow, it may not be feasible logistically because it concerns too few people.”

Dominik E. Froehlich

This means: Your target population should be neither too general nor too specific. You’ll now learn how to find the perfect balance.

Step 1: Define the target population precisely

Before you begin choosing your sample, you need to clarify who is actually relevant to your research. To do this, it helps to take a close look at your research question.

1.1 Which people are relevant to your research?

Think about this:

  • Who has knowledge or experience related to your topic?
  • Who is affected by your research question?
  • Are there specific demographic characteristics (age, gender, profession, education, etc.) that play a role?
  • Which people would be particularly interesting for your analysis?

If, for example, you are examining brand perception in sustainable fashion, your target groups could be:

  • Young adults between 18 and 30 who shop with environmental awareness
  • People who regularly buy sustainable brands
  • People who work in the fashion industry

1.2 Narrowing down the target group

If your target group seems too large, you can narrow it down further:

  • By location: Focus on a specific region or city
  • By interests: Survey people with specific consumption habits
  • By profession: Only people from a specific industry

If your target group is too small, you can expand it by including related groups.

“Sometimes the perspective is also quite interesting. I could ask the question from the perspective of buyers or sellers. That is a very different question because I would be asking different people.”

Dominik E. Froehlich

So think carefully about which perspectives you would like to consider your topic from!

Step 2: Determine the appropriate sample

Once you know who you want to survey, the question is how many people you need.

2.1 Determining the sample size

The optimal size of your sample depends on several factors:

  • Research method: Quantitative studies often require larger samples than qualitative studies
  • Expected differences: If you have many comparison groups, you need larger samples
  • Resources: Time and budget play a major role

The following figures can help you find your bearings:

  • Qualitative interviews: 10–30 people
  • Online surveys: At least 100, preferably 300–500 participants
  • Expert interviews: 5–15 people

My tip: If you need a large sample but cannot find enough participants, you can consider alternative methods such as secondary data or field studies.

2.2 Random or purposive sampling?

Depending on how you select your sample, there are various methods:

Random selection (probability sampling):

  • Every member of the population has an equal chance of being included in the sample
  • Advantages: Objective and representative
  • Examples: Simple random sampling, stratified sampling

Purposive selection (non-probability sampling):

  • The sample is deliberately selected to represent specific groups
  • Advantages: More practical when random selection is not possible
  • Examples: Expert sampling, snowball sampling

If you are conducting an empirical study, you should carefully consider which method is the best fit!

Step 3: Practical tips for sampling

To ensure that your sample selection is successful, keep the following points in mind.

sample

3.1 Avoid bias

There are many pitfalls that can distort your research findings:

  • Self-selection: When only particularly interested people participate
  • Undercoverage: When important groups are missing
  • Social desirability: When participants give answers they believe are “correct”

So think about how you can obtain objective and unbiased data!

3.2 Allow enough time

Recruiting participants often takes longer than expected. If you have difficulty finding participants, use several channels:

  • Social media such as Instagram, X, LinkedIn, Xing, TikTok, …
  • University forums
  • Email distribution lists
  • Your personal networks of friends, family, and acquaintances

3.3 Ask the right questions

It is not only whom you interview, but also how you ask that matters. Make sure your questions are:

  • Formulated in a clear and understandable way
  • Not suggestive or judgmental
  • Relevant to answering your research question

“The idea is simply that you have a research question that is somewhat modular, so that you have flexibility in the research process.”

Dominik E. Froehlich

Flexibility is especially important if your research takes an unexpected direction!

Conclusion: Finding your perfect sample

Choosing the right target population and sample is crucial to the success of your research. Think carefully about whom you want to survey, how large your sample needs to be, and which sampling method is the best fit.

If you are unsure, try out different options and adapt your method if necessary. Good planning will save you a lot of stress later on!