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Problem Solving & Quality · Sustain

Effectiveness Check

Compare the indicator before and after the countermeasure over the period agreed at the start, and close only if the gain is real and stable.

  • Time30 min
  • FormatSolo
  • StageSustain

Effectiveness Check: what it is and why it works

An effectiveness check verifies that a corrective action actually solved the problem, not just that it was implemented. It compares the indicator before and after the countermeasure, over a period and against closure criteria that were agreed at the start of the problem-solving effort, using the same measurement method both times. It also confirms that the result holds after temporary containment, such as extra inspection or sorting, has been removed, and it looks for side effects on other indicators.

Many organizations close corrective actions when the tasks are done, without looking at whether the problem went away. This is one of the main reasons the same problems return. An effectiveness check asks a simple question with data: is the improvement real, stable and caused by the fix? A run chart or control chart shows whether the shift is clear or just a good week. If the criteria are not met, the right response is usually to revisit the root cause rather than pile on more actions. ISO 9001 requires reviewing the effectiveness of corrective actions, and D6 of an 8D asks for the same. A confirmed result feeds the lessons learned register.

What you need

  • The closure criteria and baseline defined at the start
  • The indicator, measured with the same method before and after
  • The implementation date and details of the countermeasure
  • Information on when containment was removed
  • Data on potential side effects, such as downtime, energy or cost

What you get

  • A before and after comparison on a chart
  • A decision: close, extend the observation period, or reopen root-cause analysis
  • Confirmation that the result holds without containment
  • Findings on side effects and a closure record

When to use it

When actions are marked “done” but nobody looked at whether the problem went away.

How to do it, step by step

  1. Take the closure criteria and the baseline written at the start.
  2. Collect the indicator after implementation over the agreed period, with the same measurement method.
  3. Compare before and after on a run chart or control chart; check that the shift is clear, not just a lucky week.
  4. Verify that containment has been removed and the result still holds without it.
  5. Close formally if criteria are met; if not, reopen the root-cause analysis — do not simply add more actions.

Worked example: Label misalignment on a bottling line

Illustrative scenario — figures are realistic but not from a real company.

A beverage bottling line had a label misalignment rate averaging 1.8 % of bottles, detected by a camera system and rejected. The root cause was bottle wobble at the labeler infeed, and the fix was a new set of guide rails and a star-wheel adjustment. The closure criterion, set at the start, was a rejection rate below 0.5 % for eight consecutive weeks, with containment, a second manual check at the packer, removed for at least four of them.

  1. The engineer extracted weekly reject rates from the camera system for 12 weeks before and 8 weeks after the change, with no change to the camera settings.
  2. A run chart showed a clear drop, from weekly values between 1.5 % and 2.2 % to values between 0.3 % and 0.5 %. The shift was far larger than normal week-to-week variation.
  3. The manual packer check was removed in week four after the change; the reject rate did not rise during the following four weeks.
  4. Side effects were checked: line speed was unchanged, but star-wheel changeover took ten minutes longer due to the new adjustment, a cost the team accepted.

Result. The criteria were met, and the corrective action was formally closed with the chart attached. The labor for the manual check was reassigned. The longer changeover was noted as an improvement opportunity for the next project. The team recognized that the closure criteria agreed at the start made the decision straightforward.

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Common pitfalls and how to avoid them

  • Closing the action when the task is complete rather than when the result is confirmed.Separate implementation status from effectiveness status and close only on data.
  • Checking too early, over a period too short to see normal variation.Use the observation period agreed at the start, long enough to include shifts, batches or seasons.
  • Keeping containment in place during the check, which masks whether the fix works.Remove containment deliberately during the check, with a plan to restore it if the indicator rises.
  • Responding to a failed check by adding more actions to the list.Reopen the root-cause analysis; a fix that did not work suggests the cause was not correctly identified.

Frequently asked questions

How do you verify the effectiveness of a corrective action?

Compare the problem indicator before and after the corrective action, using the same measurement method, over a period long enough to see normal variation. Check the result against the closure criteria agreed at the start, confirm that it holds after containment is removed, and look for side effects. A run chart or control chart makes the comparison clear.

How long should you wait before checking effectiveness?

It depends on how often the problem occurred. For a frequent defect, a few weeks of data may be enough; for a rare failure, you may need months, or use an indirect indicator such as a process parameter linked to the cause. The period should be agreed when the closure criteria are set, not chosen after results come in.

What does ISO 9001 require for corrective action effectiveness?

ISO 9001 requires organizations to review the effectiveness of any corrective action taken, as part of the nonconformity and corrective action clause. It does not prescribe a specific method, so each organization decides how to demonstrate effectiveness. Auditors typically look for objective evidence that the problem did not recur, not just proof that actions were completed.

Origin

Verification of effectiveness — 8D discipline D6; corrective-action requirement of ISO 9001 (clause 10.2).

Related methods

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