Detailed Explanation:
The correct answer is D. Automating machine settings and locking out operator-controlled machine settings.
Poka-yoke means mistake-proofing. Its purpose is to prevent errors from occurring or to make them immediately impossible or obvious. In this case, the defects are being caused by operators tampering with machine settings. The most effective poka-yoke solution is to remove the opportunity for that error by automating the settings and locking out operator access.
This is true mistake-proofing because it:
Prevents the error at the source
Removes dependence on operator judgment in a critical control point
Reduces process variation
Improves consistency and defect prevention
Why the other options are incorrect:
A. Form a process improvement team to drive waste from the process
This may support broader improvement, but it does not directly mistake-proof the specific cause of defects.
B. Additional tracking of errors and outputs from the process
Tracking is a monitoring activity. It detects trends after errors occur rather than preventing the error itself.
C. Adding additional inspection to the process
Inspection is a detection method, not a prevention method. Poka-yoke focuses on preventing mistakes rather than finding them later.
Quality Management Excellence reference basis:
This answer is aligned with Quality Management Excellence principles of:
prevention over detection,
control at the source,
reducing variation,
and designing processes so that errors cannot easily occur.
Mistake-proofing is a strong excellence practice because it improves process reliability by eliminating the possibility of known human-error pathways rather than depending on inspection or rework.
