A finished fishbone diagram can look convincing, which is exactly why it needs a reality check.
Key Concept
Everything on a fishbone diagram is a hypothesis, not a fact. Acting on a guess can waste money and leave the real problem untouched. Evidence from measurements, observation, or a small test is what turns a suspect into a confirmed root cause.
Practical Example
The bakery team ranks "oven runs cool in the morning" and "proofing shortened on busy days" as the top suspects. They place a thermometer inside the oven and log the temperature every morning for a week. During the first hour the oven sits about 15 °C below the dial setting, and the pale loaves line up with those mornings. The proofing logs show no pattern, so that cause is set aside for now.
Standard Procedure
- 1Pick the few causes that seem most likely or most damaging.
- 2Decide how each one can be checked: measure, observe, compare, or run a small test.
- 3Collect the evidence.
- 4Confirm or eliminate each cause based on what the evidence shows.
- 5Fix the confirmed cause, then keep tracking the original problem to see whether it truly improves.
Lesson Summary
- ✓The fishbone diagram suggests where to look; data tells you what is true.
- ✓Eliminating a cause with evidence is progress, not failure.
- ✓Always track the problem after a fix to prove the fix worked.