Certified Six Sigma Black Belt Exam General 4 — Questions and Answers
Question 1: A Black Belt applies the 5 Whys technique during a problem-solving session. What is its primary limitation?
- It can only identify a single root cause
- It requires expensive software tools
- It relies on team knowledge and can lead to different root causes depending on participants (Correct answer)
- It is only applicable to manufacturing processes
Correct answer: It relies on team knowledge and can lead to different root causes depending on participants
The 5 Whys is subjective and team-dependent, meaning different groups analyzing the same problem may arrive at different root causes.
Question 2: In the context of Statistical Process Control, what does the Western Electric Rule 2 (also called the '2-of-3 rule') detect?
- A single point beyond 3 sigma
- Two of three consecutive points beyond 2 sigma on the same side of the centerline (Correct answer)
- Eight consecutive points on one side of the centerline
- Six consecutive points trending in one direction
Correct answer: Two of three consecutive points beyond 2 sigma on the same side of the centerline
Western Electric Rule 2 flags a potential shift when 2 of 3 consecutive points fall beyond the 2-sigma warning limit on the same side of the center line.
Question 3: Which of the following best describes the purpose of a SIPOC diagram in the Define phase?
- To map detailed process steps at the floor level
- To provide a high-level view of the process and identify key stakeholders and boundaries (Correct answer)
- To quantify defects per unit across the supply chain
- To identify critical-to-quality characteristics from customer surveys
Correct answer: To provide a high-level view of the process and identify key stakeholders and boundaries
A SIPOC diagram gives project teams a macro-level view of the process, capturing Suppliers, Inputs, Process steps, Outputs, and Customers to establish scope.
Question 4: What does 'confounding' mean in the context of a fractional factorial experiment?
- A factor's effect is split across multiple blocks
- Two or more effects cannot be estimated independently because they are aliased with each other (Correct answer)
- An interaction term is statistically insignificant
- Replication increases the experimental error
Correct answer: Two or more effects cannot be estimated independently because they are aliased with each other
Confounding (aliasing) occurs when the design cannot distinguish between two effects because they are mathematically identical in the chosen fraction of the experiment.
Question 5: A Black Belt calculates a p-value of 0.02 for a hypothesis test with α = 0.05. What is the correct conclusion?
- Fail to reject H₀; there is insufficient evidence of an effect
- Reject H₀; the result is statistically significant (Correct answer)
- Accept H₁; the alternative hypothesis is proven true
- The test is inconclusive; repeat with more samples
Correct answer: Reject H₀; the result is statistically significant
Since p (0.02) < α (0.05), there is sufficient evidence to reject the null hypothesis; the result is statistically significant at the chosen significance level.
Question 6: In a value stream map, which symbol typically represents a 'push' system between process steps?
- A pull arrow
- A kaizen burst
- A push arrow (straight arrow) (Correct answer)
- A triangle with an 'I' for inventory
Correct answer: A push arrow (straight arrow)
A straight push arrow in a value stream map shows that material is pushed downstream to the next process regardless of whether it is needed, often creating inventory.
Question 7: Which quality cost category includes expenses for rework, scrap, and warranty claims?
- Prevention costs
- Appraisal costs
- Internal failure costs and external failure costs (Correct answer)
- Conformance costs
Correct answer: Internal failure costs and external failure costs
Rework and scrap are internal failure costs (defects found before delivery), while warranty claims are external failure costs (defects found after delivery).
Certified Six Sigma Black Belt Exam General 4
A Black Belt applies the 5 Whys technique during a problem-solving session.
What is its primary limitation?