Interview Sampling: How do I find people to interview?

In this six blog post series, we cover the best practices in interviewing, from preparation, to analysis. The following is the second blog post, finding people to interview.

Table of Contents

1. An Introduction to Research Interviews
2. Interview Sampling: How do I find people to interview? (You are here)
3. Good questions to ask while interviewing
4. Interview techniques and how to record interviews
5. Transcription: How to transcribe interviews?
6. How to analyze qualitative interviews?

How to find people to interview and how to get their consent?

Finding participants to interview is the first major milestone in the interview process. First task is to figure out who to interview. Usually the research question specifies the participants. For example, a research question on the doctors' perception of their working conditions naturally suggests that doctors will make up the participant group. Following this example, doctors is the "population" this study based on. You can narrow this down to "all doctors in my town", or narrow it even further to "emergency room doctors in southern Stockholm".

After deciding on the population, the next task is to draw participants from this population, which will be our "sample". The doctors you interview in the end is your sample.

How many people should be in your sample?

Although there is no fixed answer to this question, there is a rule of thumb. As an interviewer, once you start anticipating the answers you will get, and you don't hear anything interesting anymore, you should probably stop interviewing.

Some knowledge on sample types is also helpful to get through the sampling question.

1. Convenience sampling: asking people who you think are most likely to agree for an interview.
2. Stratified sampling: If your population has specific sub-groups, such as age groups, class, gender, experience, etc., you might consider selecting equal numbers from each group. This would make your interview sample stratified.
3. Snowball sampling: If you get a hold on some interviewees, you can consult their networks to ask around who is willing to participate in your interviews.

As an interviewer you don't need to chose only one method of sampling but can mix and match, for example use stratified sampling and snowballing method.

What happens if it doesn't work?

If you can't get hold on the people in your population, then you should either redefine your population or even change your research question.

How do I get people to agree to be interviewed?

Once you decide on the interview type and the population, you can contact the potential interviewees.

According to GDPR regulations, any research interview should have a consent form which is a part of ethical way of interviewing.

A comprehensive consent form should include:

• Who you are
• The aim of your research
• What your research is about
• Why you are doing interviews
• How the interview data will be stored
• How the data and information collected will be used

Consent forms are given before starting the interviews, and inform the participants with the basic information, their rights and privacy. As part of the research ethics, the form should explain when and how participants can withdraw their data from the research, if they wish to, during and after the interview.

Once you have chosen the people to interview, it is time to start preparing yourself. For a comprehensive guide on interview questions to ask, check out our next blog post: Good questions to ask while interviewing.