One-on-one interviews – also known as in-depth interviews or IDIs – are a versatile and invaluable tool in the ever-evolving landscape of research methodologies. They allow researchers to dive deep into the minds of their subjects, gaining insights that go beyond quantitative data.

But when is the right time to use interviews in applied research, and why should you consider them a crucial part of your practice? 

This article answers these questions, and explores the "when" and "why" of using interviews in research.

The role of interviews in research

Let's establish the role user interviews play in the research process. Interviews are a qualitative data collection method that involves direct, live interaction with participants. They can take various forms, such as structured, semi-structured, or unstructured, depending on the research objectives (more on this below). 

Here's why interviews are so valuable:

• In-depth learning: Interviews allow you to gather rich, detailed information from participants. They provide a deep understanding of their experiences, perspectives, and emotions.

• Contextual understanding: Interviews can uncover the context in which participants' thoughts and actions are embedded. This is often hard to capture through surveys or quantitative data alone.

• Flexibility: The flexibility interviews provide enables you to adapt your approach based on the evolving needs of your study. This allows for exploration of unanticipated themes and the addition or omission of questions in real time.

• Participants’ voice: Interviews give participants a voice to share their stories and experiences, allowing them to feel heard and valued in the research process. You also gain an understanding from hearing the words, phrases, and descriptors they choose to use in their responses.

What’s the difference between structured, semi-structured, and unstructured interviews?

Structured, semi-structured, and unstructured are different approaches to conducting interviews in user research. They each offer distinct levels of formality and flexibility.

Structured interviews

• Description: In structured interviews, the questions and the order you ask them are predetermined and standardized. Akin to a survey, you follow a rigid format, ensuring consistency across all interviews.

• Purpose: This method is suitable when you want to gather specific, quantifiable data, such as time on task. It allows for easy comparison between responses, as all participants are asked the same set of questions in the same order.

• Advantages: 

  • Provides reliable and comparable data. 

  • Reduces interviewer bias.

  • Facilitates statistical analysis.

Semi-structured interviews

• Description: Semi-structured interviews have a set of predetermined questions, but the moderator has the flexibility to explore topics in-depth and adjust the questioning based on participant responses.

• Purpose: Balancing structure with flexibility, semi-structured interviews are valuable when you want to dive deep into certain areas while maintaining a standardized core set of questions. Most interviews I conduct fall into this category.

• Advantages: 

  • Offers a balance between structure and flexibility. 

  • Allows for in-depth exploration. 

  • Permits adaptation to individual responses.

Unstructured interviews

• Description: Unstructured interviews are open-ended and lack a predetermined set of questions. The conversation flows naturally, guided by the participant's responses and your curiosity.

• Purpose: Ideal for exploring new or complex topics where you want to discover unexpected learning. It offers a more conversational and free-form approach.

• Advantages: 

  • Encourages exploration of new ideas in an “anything goes” sort of way. 

  • May provide a deeper understanding of participants' perspectives. 

  • Allows for more free-form discovery.

Now that we appreciate the significance of interviews, and the different forms they can take, let's explore when and why to use them in research.

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Why use interviews in research?

There are number of reasons to use interviews in your research, for example:

• Human-centered learning: Interviews focus on the human element of research. They help you ‌connect with participants on a personal level, uncovering motivations, attitudes, belief systems, and feelings.

• Rich data: Interviews provide data that’s rich in context, meaning, and nuance. This depth of information can lead to a more comprehensive understanding of the research subject.

• Flexibility: The adaptability of interviews allows you to pivot your questions and approach based on the participant's responses. This flexibility can lead to unexpected and valuable insights.

• Participant empowerment: Interviews empower participants by giving them a voice in the research process. This can lead to more candid and honest responses.

When to use interviews in research

Below is a guide on when to use interviews depending on what your research goals are.

Exploration and understanding

Use interviews at the beginning of your research when you want to explore a new or poorly understood topic or segment. They can help you generate hypotheses and assumptions, as well as refine your research questions, terminology, problem areas, and opportunity spaces.

Example: Conducting semi-structured interviews with potential users to explore their needs, challenges, and expectations before developing a new product. You can gather insights that shape the initial direction of the project.

Complex phenomena

When your research involves complex or multifaceted phenomena, interviews can provide a deeper understanding of these intricacies. They help unravel the layers of a subject.

Example: Investigating the adoption of a new technology within a specific industry. Through interviews with professionals, you can understand nuances influencing the technology's adoption, including organizational structures, user behaviors, and external influences.

Contextual research

If you need to study a topic within its specific context, interviews are the go-to method. They can offer insights into how external factors affect the subject of your study.

Example: Studying the usability of a coffee maker by interviewing participants in their homes. This approach can provide learning into how external factors, such as the user's surroundings and daily routines, can impact their interactions with the product.

Validation and confirmation

Interviews are valuable for confirming and validating findings from other research methods, such as surveys or A/B tests. They provide an opportunity for participants to explain or clarify their responses, helping us understand “why”.

Example: After running a usability test on a website interface, conduct follow-up interviews with participants to validate the quantitative data. Interviews help confirm whether observed issues align with their perceptions and experiences, providing a more holistic understanding.

In-depth exploration

When your research aims to explore individual experiences, emotions, or perspectives, in-depth interviews are the ideal choice. They allow participants to express themselves freely.

Example: Exploring the emotional journey of applying for college scholarships. In-depth interviews can uncover individual experiences, emotions, and perspectives, allowing for a nuanced understanding of the challenges and support needed during this journey.

Unlocking user insights with interviews

Interviews have become indispensable for their ability to uncover nuanced findings, and ideally insights, and provide a voice to participants. Knowing when and why to use interviews in your research is the key to unlocking the potential of this powerful approach. 

Whether you're exploring a new topic, trying to understand or validate findings from another study, or seeking to understand the human experience, interviews offer a wealth of opportunities to enhance your research endeavors. So, consider interviews as a valuable addition to your research toolkit and watch your depth of understanding soar to new heights.

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This article was authored by Michele Ronsen, Founder and CEO of Curiosity Tank. Michele is a user research executive, coach and educator. She teaches design and user research to people around the world. Her corporate trainings and workshops are inspired by working with Fortune 500s and start-ups for more than twenty years. Fuel Your Curiosity is her award-winning, free, user-research newsletter. In 2020, LinkedIn honored Michele with a TopVoices award in the Technology category. She is the first and only researcher to receive this award.