Cause and Effect Diagrams

in Health Care, Tools & Methods, Videos

By David M. Williams, PhD

Harvardx course Practical Improvement Science in Health Care with the Institute for Healthcare Improvement.

A common challenge for improvement teams is identifying what changes you can test to improve a process or problem. One great method to help you break down ideas is a tool known as a “cause-and-effect diagram.” You may have also heard of this tool referred to as an “Ishikawa diagram” — attributed to its creator, Kaouru Ishikawa — or a “fishbone diagram” because of the resemblance to the bones of a fish.

To create a cause-and-effect diagram, write the effect in a box on the right-hand side of the page. So let’s imagine we’re working on improving hand-washing. All right. Then draw a horizontal line across the page. Decide on a few categories or causes for the problem. Useful categories of causes in the classic fishbone diagram include people, methods, materials, equipment, and environment. Then we can draw a diagonal line to each of these, and these are actually the bones of the fish — and hence, its name.

The process of categorizing potential causes may be very useful to help you to break down a complex problem and focus in on it from various perspectives. So as you’re looking at each of the categories, you want to generate a list of causes. In this example, people might include clinical staff. All right. It also might include non-clinical staff. Let’s put them as just “other staff.” It might include the methods. How do you actually wash your hands? I’ll say “wash process.” It could be the materials. Are you using the right kind of soap, or does it dry out your hands? So we’ll think about the soap. It could be the equipment, like the dispenser. Is there an easy dispenser to use? Does it give you the right amount? Or maybe it’s the environment. Where is the dispenser location? Is it near the process of care?

Identify the causes by asking why with people that are closest to the process until you’ve reached a useful level of detail. That is when the cause is specific enough to be able to test a change and to measure its effects. Sometimes, I like to describe this for folks that have children as the five-year-old method. If you ever had a kid, they asked you “why” five times constantly until they get to the root of the problem. And you’re doing the same thing here.

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