Invalid assumptions are the root of most business failures. It’s important our students understand how easy it is for everyone, including them, to make them.

In just 15 minutes, this interactive exercise will help your students understand why they need to validate their business assumptions.

Winner of the 2019 Excellence in Entrepreneurship Exercises Competition

We introduced this exercise to our community here as part of a larger series of exercises. You all helped us tweak the exercise into a format that won the Excellence in Entrepreneurial Exercises Competition at USASBE 2019!

Given the success of this exercise, we wanted to provide an overview so you know how and why you might engage your students with this exercise.

Overview

We have two goals with the Toothbrush Design Challenge exercise:

1. Give your students the experience of making hidden assumptions
2. Help your students learn why it’s so important to validate assumptions

For more details on this exercise, check out this lesson plan.

The Exercise

Form teams of 3 or 4 students. Give each team an adult toothbrush.

Their assignment is to design a child’s toothbrush. The design must include at least the following elements:

1. Color scheme
2. Dimensions

The color scheme element is really a red herring. The colors they choose are irrelevant. We include the color scheme requirement to ensure students are not solely focused on the dimensions element. The dimensions are where students will unearth hidden assumptions, and create an ineffective product based on those hidden assumptions.

Hidden assumptions will likely cause students to design a toothbrush with the wrong dimensions for children. They will assume a smaller hand needs a smaller toothbrush.

Display the slide below that contains hand size data. Give students 3 minutes to design a child’s toothbrush.

The Debrief

After 3 minutes, ask teams whether their child’s toothbrush was larger or smaller than an adult’s. Most teams will end up making a smaller toothbrush. This is a very natural and logical assumption based on the hand size data we presented them. It is the assumption very experienced product designers at toothbrush manufacturers made, so your students are in good company!

Your students likely designed a child’s toothbrush that would fail in the market based on hidden assumptions. Show this video, where IDEO partner Tom Kelley drives home the importance of acknowledging and testing hidden assumptions:

Reflect on what hidden assumptions they made, and why they made them. Point out that many toothbrush manufacturers made the same invalid assumptions many of them made in terms of a smaller hand needs a smaller toothbrush.

Discuss how students could test their assumptions to determine their validity. Steer them toward observing customers using a product or service, and toward prototyping the product or service.

This exercise is fast, fun, and engaging for students. We designed it as a flexible experience that you can use to introduce various topics, such as:

1. Why companies fail
2. Planning vs. experimenting
3. Business model canvas

If you want to introduce your students to a curriculum of these kind of award-winning experiential exercises, request a preview of our ExEC curriculum here.