Build a FLEX – Validate Stage

Start with your Riskiest Assumption

A good experiment starts by defining exactly what you believe to be true, so you can craft a way to test it.

In the Validate stage, there are two primary assumptions to be tested. Your Fluency Score report may indicate one or both need further testing.

  • What do you believe is true about the problem you want to address?
  • What do you believe is true about who experiences that problem?

Clearly state your assumption about the problem and the customer in the riskiest assumption field.

Protip #1: Watch out for solutions pretending to be problems. A good problem assumption can be solved in dozens of ways completely unrelated to the solution you have in mind.

Protip #2: Don’t define the customer by a demographic persona (moms between ages 25-44). Instead, use early adopter behaviors to organize your thinking for the customer.

Example: Owners of large dogs who visit the dog park 3+ times per week don’t have a good  way to keep their dog clean.

Next, design a tiny, fast experiment

Design a tiny, fast experiment that will give you immediate data toward validating or adjusting your riskiest assumption.

  • Measure one thing at a time
  • Constrain the experiment so it can be completed within one sprint (usually a week)
  • Formulate a falsifiable hypothesis – it has to be possible to learn you are wrong
  • Make sure you can correlate results to specific actions

Protip #1: To test a Validate stage assumption, you will conduct customer discovery interviews. Only talking directly with (potential) customers can you discover whether these particular early adopters experience the problem you are working on and understand how they think about that problem.

Protip #2: You will likely be very, very right in your hypothesis or very, very wrong. Just a small handful of interviews will give you the data you need. Plan to conduct 3-5 interviews in a single sprint.

Example: If I interview five owners of large dogs who visit the dog park 3+ times per week, at least three of these early adopters will verbalize the problem.

Then, determine your action steps.

Get super clear on exactly what needs to be accomplished in order to complete this experiment.

Do you need to research people you could contact to set up an interview? What preparatory steps might be necessary before you begin interviewing?

If this is your first Validate FLEX, be sure to include watching the Customer Discovery videos as part of your action steps. These videos will help prepare you to develop high quality questions and to conduct the interviews effectively.

Protip #1: If you use any kind of task management system (to do list, trello etc), be sure to add these action steps to your normal work planning.

Protip #2: It is common to procrastinate on these action steps, but you may be waiting on other people to get the interviews scheduled. Make it a priority to get started on any prep work immediately.


  • Watch the four Validate stage videos
  • Complete the SCALE exercise
  • Develop five CDI questions
  • Schedule five interviews
  • Conduct five interviews
  • Write results in FLEX planner

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Fluent Library Resources

You want customers who will chase you down the street with cash…

You may be addressing a massive market, but right now, you need to focus on your early adopter customers. This video provides a powerful framework for identifying and organizing your thinking about this beachhead segment. 

Do you have several types of customers who could be early adopters?

Identifying early adopters through the customer discovery process can often be iterative. You run several sprints, testing and adjusting the early adopter profile. This SCALE exercise can help you move faster.

Customer Discovery Interviewing – Pt 1

There’s no better source for validating your assumptions about your customers and the problems they experience than by talking directly to them. This video introduces key best practices for conducting these interviews.

Customer Discovery Interviewing – Pt 2

Developing effective customer discovery questions is key to validating your assumptions in this stage. This video covers best practices for conducting interviews with non-leading, problem- and customer-focused questions.