Research Methods · Customer Discovery · Contextual Inquiry · PTOS

Discovery Tools: When to Use Customer Interviews, Contextual Inquiry, and Diary Studies

A practical overview of key Discovery research methods: Customer Interview, Contextual Inquiry, and Diary Studies. Learn which tool is right for your situation and how to use it effectively.

Discovery Tools: When to Use Customer Interviews, Contextual Inquiry, and Diary Studies

The Discovery process is not about "gathering opinions," but about producing clarity on real user problems. To get quality insights, it's important to choose the right tool for each situation. There's no universal method, but there is a simple logic of choice that will help you avoid mistakes.

Here are three key Discovery methods and the situations in which each is most effective.

1. Customer Interview

What it is: A deep conversation with a user, focused on their past experiences, problems, and behavior. The key principle is not to ask about the future ("would you buy this?"), but to analyze specific situations from the past ("tell me how you solved this problem last time"). The ideal framework for this is "The Mom Test".

• When to use: You have data that shows what is happening, but you don't understand why. For example, analytics show a high drop-off at a certain step in the funnel.
• Process:
  1. Find the "breaking point" in the data (funnels, cohorts).
  2. Conduct 5–8 interviews with users from this segment to uncover the mechanism of the problem.
• Why it works: Interviews help explain the numbers with real stories, context, and user motivation.

2. Contextual Inquiry

What it is: Observing a user in their natural environment, "in action." You watch how a person actually works and ask clarifying questions along the way.

• When to use: When behavior and context are more important than anything, and a person might miss important details when just talking. Especially effective for complex B2B products or internal tools.
• Process:
  1. Arrange with the user to observe their workflow.
  2. Sit next to them (physically or virtually) and observe silently.
  3. Ask questions only when you see something unexpected, complex, or an interesting workaround.
• Example: You thought the problem was with a button, but after 40 minutes of observing an accountant, you realized the real pain is manually consolidating data from three different systems before clicking that button.
• Why it works: This method uncovers the "invisible" work that people often forget to mention in a regular interview.

3. Diary Studies

What it is: A method where users, over a certain period (from a few days to a few weeks), independently record their behavior, thoughts, and feelings related to a specific scenario.

• When to use: When the problem is related to a habit, repetition, or contextual breakdowns. For example, you want to understand how people form a habit of exercising, why they forget to take medication, or how their mood changes throughout the day.
• Process:
  1. Give users a simple task and a tool for recording (a chatbot, a form, a notebook).
  2. Ask them to make short entries several times a day or when a specific event occurs.
  3. After the study is complete, conduct a final interview to review the entries and clarify details.
• Why it works: Diaries allow you to collect data on behavior "over time and in context," which is impossible to obtain in a one-time interview.

Bonus Method: Jobs-to-be-Done (JTBD)

• What it is: This is not so much a method as a "lens" through which you look at user motivation. JTBD focuses not on who the user is, but on what "job" they are "hiring" your product to do to make progress in their life.
• When to use: When you need to understand the deep motivation for a choice, especially in a competitive environment. Why does a user choose your product over a competitor's or a good old Excel spreadsheet?
• Why it works: JTBD helps shift the focus from demographics and attributes to the real progress the user is looking for.

By choosing the right tool for each situation, you will stop guessing and start getting real, actionable insights that will become a solid foundation for your product decisions.