David Williams, Executive Director, IHI

Understanding variation is critical when you’re working to improve a process or system. In this activity, you’ll learn to distinguish between two types of variation: common cause and special cause. (And you’ll get to eat candy!)

In the first video, David Williams explains how to participate in the activity. In the second video, he talks with Afiesha McMahon, IHI Senior Project Manager, about what the candy counting game teaches us about variation and how these lessons apply in the real quality improvement work. You can show these videos in a group setting to help you facilitate this activity or watch them by yourself ahead of time. 

Part 1: How to Do the Candy Counting Activity                          

Read the video transcript.

Part 2: What We Learn in the Candy Counting Activity   

  Read the video transcript.

Learning Objectives: At the end of this activity, you will be able to:

• Define common cause variation and special cause variation.
• Discuss why knowle​dge of variation is important when working to improve a process or system.

Discussion Questions:

1. Think of a work process you’re familiar with. What would be an example of common cause and special cause variation in this process?
2. Why is understanding variation useful when you are trying to improve a process or system?
3. Imagine you’re working on an improvement project and you notice a data point that’s far outside the normal range of variation. What would be your first course of action?