Lean Six Sigma Yellow Belt Certification Control and Sustainment Methods 4 — Questions and Answers
Question 1: Poka-yoke devices are used in the Control phase primarily to:
- Speed up production rates
- Prevent defects by making errors physically impossible or immediately detectable (Correct answer)
- Reduce training time for new hires
- Replace statistical process control charts
Correct answer: Prevent defects by making errors physically impossible or immediately detectable
Poka-yoke (mistake-proofing) designs the process or tooling so errors either cannot occur or are caught immediately before becoming defects.
Question 2: Visual management tools, such as shadow boards and floor markings, support sustainment by:
- Reducing the number of employees needed
- Making the standard condition instantly visible so deviations are obvious (Correct answer)
- Automating the control chart updates
- Replacing the need for a control plan
Correct answer: Making the standard condition instantly visible so deviations are obvious
Visual management makes the correct state of the workplace or process immediately apparent so anyone can see at a glance when something is out of place.
Question 3: A warning poka-yoke differs from a control poka-yoke in that it:
- Prevents the error from occurring physically
- Alerts the operator to an error but does not stop the process automatically (Correct answer)
- Only works on automated assembly lines
- Measures defect rates over time
Correct answer: Alerts the operator to an error but does not stop the process automatically
A warning poka-yoke (e.g., an alarm or light) signals that an error has occurred, while a control poka-yoke physically prevents the error.
Question 4: Which of the following is the strongest form of mistake-proofing?
- Operator self-inspection checklists
- Physical design that makes incorrect assembly mechanically impossible (Correct answer)
- Color-coded work instructions posted at the station
- Automated alerts sent to a supervisor
Correct answer: Physical design that makes incorrect assembly mechanically impossible
Physical design changes (e.g., asymmetric connectors) are the strongest poka-yoke because they eliminate the possibility of error regardless of operator attention.
Question 5: A visual control is effective in sustainment when it:
- Requires a supervisor to interpret the information
- Communicates process status to anyone who looks, without explanation (Correct answer)
- Is updated only during monthly audits
- Is located in the manager's office
Correct answer: Communicates process status to anyone who looks, without explanation
Effective visual controls are self-explaining — anyone walking past the area should immediately understand whether the process is normal or abnormal.
Question 6: An andon light system in a manufacturing cell is an example of which sustaining tool?
- SPC chart
- Visual management / visual control (Correct answer)
- Control plan
- FMEA
Correct answer: Visual management / visual control
An andon is a visual (and sometimes audible) signal that displays process status and alerts operators and team leads to abnormal conditions.
Question 7: Which scenario best illustrates a successful poka-yoke implementation?
- A checklist requiring the operator to verify part orientation before assembly
- A connector designed so it can only be inserted in the correct orientation (Correct answer)
- A supervisor inspecting each unit after assembly
- A control chart monitoring daily defect counts
Correct answer: A connector designed so it can only be inserted in the correct orientation
A connector that physically can only go in one way prevents mis-assembly without requiring operator attention, making it a true mistake-proof design.
Lean Six Sigma Yellow Belt Certification Control and Sustainment Methods 4
Poka-yoke devices are used in the Control phase primarily to: