Framework library · Decision making and problem solving
Fishbone diagram
A fishbone diagram puts the problem at the head and the possible causes along bones grouped by category. It makes a team look in every direction before it settles on a cause, because each category prompts causes nobody had mentioned. It produces candidate causes, not answers: the strongest candidates then need data.
Use it when
- A problem probably has several contributing causes and the team is fixed on one of them.
- People in different functions each blame another, and you need every candidate cause on one page.
- You are about to collect data and need to decide what to measure.
Avoid it when
- You already have counts or costs by cause. A Pareto analysis ranks them directly.
- The problem has one evident chain of cause and effect. Five whys is quicker.
- You need to assess how a process could fail before it does. Use FMEA.
How to run it
Write the problem at the head
Measured and specific: "18% of installation appointments fail at the first visit", not "installs are poor".
Choose the categories
People, process, technology, materials and data, environment, and measurement suit most service businesses, and the workbench uses these six. Another set may suit other work better, but keep to six or fewer.
Brainstorm causes into each category
Short phrases, one per line. Ask why each cause happens and add the answers as smaller causes beneath it.
Mark the causes the data supports
Pull the evidence you already have, such as job notes, failure codes and survey results, and note on each cause's line whether it is confirmed, likely or unsupported, for example "Wrong drop cable kit (confirmed)".
Choose two or three causes to test
Pick the confirmed or likely causes with the largest effect, and test them with data or a small change before paying for a fix.
Work through it
Answer the questions below, or load the worked example to see a finished one. The drawing updates as you type. Export the result as a PowerPoint deck, a Word document, an Excel workbook, a PDF or plain text.
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Mistakes to avoid
- Filling every category for the sake of it. An empty bone is a finding, not a gap to fill.
- Writing solutions as causes ("need more training"). Write the cause ("crews new to the survey tool").
- Stopping at the diagram. It lists candidates; data decides which of them matter.
- Using the measurement bone only for metrics. It also asks whether the problem is being measured correctly in the first place.
Where it comes from
Kaoru Ishikawa, who drew the first cause-and-effect diagram in 1943 and used it to help workers at Kawasaki Steel Works analyse problems, according to the Union of Japanese Scientists and Engineers. He set it out for a wide readership in Guide to Quality Control (Asian Productivity Organization; revised English edition 1976), and it became one of the seven basic tools of quality control. Source.
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Work through it with us
The frameworks here are free to use as they stand. If you would rather work through the question behind this one with us, these are the ways an engagement starts.