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Quality

Corrective actions: find the cause, not just the defect

By Review.LivePublished 3 min readHow we write

At 14:20 a foreman texts a photo from suite 506: no blocking behind the grab-bar location, again. It is the third accessible suite in six weeks with the same defect. Each time, the wall was opened, the blocking added and the corrective action verified and closed, and the next floor had the same gap.

Two cracks running down a white rendered wall.
Photo: Natalie Kinnear on Unsplash

A corrective action that only repairs the defect treats the symptom and leaves in place whatever produced it. Cause analysis asks what made the defect possible, and the answer is usually in a process — a sequence, a handoff, a missing check — rather than in one person. The US Federal Transit Administration's quality guidelines make the same point: fixing the most obvious condition may not solve the actual problem, there can be more than one root cause, and the root cause will often point to a process or system issue.

A short cause analysis

  1. State the defect as a fact: what, where, how many times and since when, not "sloppy work".
  2. Ask why, and keep asking until the answer is something you can change. The "5 whys" technique does exactly this, and five is a guide, not a rule.
  3. When an answer names a person, ask what allowed it: what they were not told, not given or not checked.
  4. When several causes may combine, draw a fishbone (cause-and-effect) diagram: the defect at the head, and possible causes sorted under headings such as methods, materials, people, equipment, measurement and environment.
  5. Test the cause against the facts: it should explain every occurrence, and removing it should have prevented them.
  6. Write two actions, each with an owner and a date: the repair of this defect, and the change that removes the cause.
  7. Check that the change worked on the next occurrences of the same work, not only on the repair.

Common mistakes

  • Stopping at "worker error", which leaves nothing to change.
  • Writing a corrective action that only repeats the repair.
  • Doing the analysis alone, without the foremen who know how the work was done.
  • Closing the action without checking whether the defect stopped.

Checklist

For each repeated defect

  • The defect stated as a fact, with count and locations
  • "Why" asked until the answer is a process you can change
  • No answer that stops at a person's name
  • One action for the repair, one for the cause
  • An owner and a date for each action
  • The next occurrences of the work checked

Check your understanding

Your analysis ends with "the installer was careless". What should you ask next?

Show the answer
Ask what made the careless result possible and let it pass unnoticed: missing information, a sequence that hid the work, a check that did not exist. Those can be changed for every installer, while carelessness gives you nothing to act on. If the same defect appears with different people, the cause is very likely in the process.

Sources

  1. Quality Management System Guidelines (2019 update), section 1.5.5, Root Cause AnalysisFederal Transit Administration, U.S. Department of Transportation · accessed
  2. 5 Whys (Lean Lexicon)Lean Enterprise Institute · accessed
  3. Fishbone (cause-and-effect) diagram, Quality ResourcesASQ (American Society for Quality) · accessed

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