Interview with Prototype

Interviews with prototypes can help you explore further questions or validate your offerings based on critical questions and hypotheses. Learn how to use them properly in Business Design sprints.

1. Overview

Customer interviews can help you explore further questions or validate your product, service, software or business model based hypotheses (see Hypotheses & Experiments template). You will use a prototype (e.g. mock-up, paper prototype, functional prototype, design prototype) to present your new product or service to customers / users in a tangible way. This allows you to see their reactions at first hand and to ask them about the reasons for those reactions. The quality of the feedback will be much higher than without showing your interviewees or letting them use a prototype. Do not ask your customers to predict their responses to future products and services. Make your ideas tangible! 

Decide for yourself how much "reality" is needed to explore your questions or to validate hypotheses. Make sure that you are not only collecting compliments. These interviews are never about instant confirmation of your ideas or smartness. It is about learning! Apart from constructive feedback, the goal of the interview is to end up with a concrete next step ("Investment" for your interview partner, e.g. financial, time, social) to ultimately see how committed interview partners are regarding your ideas. The "Investment" you ask for depends on you, your prototype / lean offerings and your interview partner. Make sure you choose your favorites in advance to define a clear outcome of your conversation. If the focus is on validating hypotheses, your storyline to present the prototype / lean offering is a sales pitch not an interview that should pave the way to the Investments you are looking for.

2. Key Elements





Introduce yourself and the purpose of your conversation. 

5 min.

"Get to know" (demographics)

Research relevant demographic information about your interview partner (e.g. age, profession, company size, position, budget etc) prior to the interview (if possible) and start with opening questions about your interview partner for a nice atmosphere: "Tell me about yourself / your job...".

5 min.

Presentation, usage & discussion of prototype

Present your prototype neutrally following a prepared storyline. Be authentic and tell them in which stage you are. Let your counterpart use the prototype by his/her own and wait for reactions. Get used to silence and avoid to fill gaps. Your interview partner might need some time to answer.

Encourage your interview partner to comment aloud and help him/her to do so with trigger questions (if necessary) to get valuable feedback about how your prototype is perceived, e.g.:

  • "What do you think about it?"

  • “What are you doing?”

  • “What do you like?”

  • “What do you dislike?”

Find out why he/she shows the reaction and keep him/her talking by asking "Why is that?". Active listening is key!

Think about topics you would like to talk about in advance and make sure you address them if your interview partner doesn't bring them up by his/her own: "Could you tell me more about...". But focus on aspects that matter (see Hypotheses & Experiments template). Make notes of verbal and non-verbal reactions.

30-40 min.

Next steps

If your interview partner did not address any next steps by his/her own during the conversation, ask him/her how you can proceed by suggesting your favorite options and see how he/she reacts.

5 min.


Close the interview by thanking your interview partner for the conversation and explain the next steps.

5 min.

3. Usage Scenarios

Customer interviews are in few cases the right method to validate hypotheses. But in many cases, it's very valuable to embed them into your experiments.

4. Instruction for Coaches

  1. Make sure that your team members conducting the interview study are trained in advance and ask the questions in the right way. The training should include among other things a role play to practice staying in a neutral position, asking "Why?" extensively to understand reactions and not defending your offering. 

  2. Don't outsource customer interviews to a market research agency. Let the project team feel the reactions and emotions of customers. Later, a professional agency may help to reach out to a larger audience.

  3. There is no time to test everything in one conversation. Focus on the most risky assumptions based on your Hypotheses & Experiments template.

  4. Take care that your team doesn't take answers they get from customers as a "holy grail" - especially when it comes to revolutionary change.

  5. Be aware that it can take some time to contact the right people and arrange dates with them. 

  6. A personal interview shouldn't last longer than 60 minutes (on the telephone not longer than 45 minutes). 

  7. The interviews should be conducted in a nice atmosphere where your interview partner can use the prototype by his/her own.

  8. The interviews should be done in pairs in order to capture the reactions from your interview partner carefully. One will lead the conversation and the other one observes the interview partner using the prototype and takes notes of verbal and non-verbal reactions. 

  9. Make sure that they don't talk about pricing until they can offer Lean Offerings.

  10. Help your team to document the results. Direct quotes help others to understand your findings later on.

  • Fitzpatrick, R.: The Mom Test (Amazon)

  • Constable, G.: Talking to Humans (PDF version)

  • Zaltman, G.: How Customers Think (Amazon)

  • Hall, E.: Interviewing Humans