Lean Six Sigma Yellow Belt Certification Root Cause Analysis 2 — Questions and Answers
Question 1: In a fishbone diagram, which category would 'outdated software version' fall under?
- Machine (Correct answer)
- Method
- Material
- Measurement
Correct answer: Machine
Software or equipment issues are classified under the 'Machine' (or Equipment) category in a fishbone diagram.
Question 2: Which of the following best describes a 'contributing cause' in root cause analysis?
- The single event that directly caused the defect
- A factor that increased the likelihood of the root cause occurring (Correct answer)
- The documented corrective action taken
- The measurement system used to detect errors
Correct answer: A factor that increased the likelihood of the root cause occurring
A contributing cause is a factor that made the root cause more likely to occur but is not the root cause itself.
Question 3: A team uses the 5 Whys and reaches a conclusion that cannot be further questioned. This ending point is called the:
- Proximate cause
- Root cause (Correct answer)
- Symptom
- Effect
Correct answer: Root cause
The root cause is the deepest identifiable cause in a causal chain that, when corrected, prevents recurrence.
Question 4: Which tool is MOST effective for visually displaying the relationship between a problem and all its potential causes?
- Control chart
- Pareto chart
- Ishikawa diagram (Correct answer)
- Run chart
Correct answer: Ishikawa diagram
The Ishikawa (fishbone) diagram visually maps a problem to its potential causes across multiple categories.
Question 5: During root cause analysis, a team discovers the defect rate increases every Monday morning. What type of cause is this likely indicating?
- Random cause
- Special cause (Correct answer)
- Common cause
- Assignable cause variation within limits
Correct answer: Special cause
A recurring pattern tied to a specific condition (Monday mornings) is a special cause of variation, not random noise.
Question 6: A process produces defects mainly due to operator fatigue during the night shift. In a fishbone diagram, this belongs under which bone?
- Machine
- Method
- Man (People) (Correct answer)
- Mother Nature
Correct answer: Man (People)
Human factors such as fatigue, training, or behavior are categorized under the 'Man' or 'People' bone of the fishbone diagram.
Question 7: What is the primary purpose of verifying the root cause before implementing a solution?
- To document the timeline for auditors
- To ensure the fix addresses the actual source of the problem (Correct answer)
- To identify who is responsible for the defect
- To calculate the cost of poor quality
Correct answer: To ensure the fix addresses the actual source of the problem
Verifying the root cause ensures resources are not wasted on solutions that address symptoms rather than the true cause.
