Certified Six Sigma Black Belt Exam Practice 4 — Questions and Answers
Question 1: A process is in statistical control but producing 15% defects. The appropriate response is to:
- Add control limits to tighten the process
- Investigate for special causes immediately
- Redesign or fundamentally change the process (Correct answer)
- Accept the process as stable
Correct answer: Redesign or fundamentally change the process
A stable but incapable process requires systemic improvement—adjusting inputs or redesigning the process—not just monitoring.
Question 2: Which tool maps the sequence of steps in a process and clearly shows both value-added and non-value-added activities?
- Cause-and-effect diagram
- Value stream map (Correct answer)
- Spaghetti diagram
- SIPOC
Correct answer: Value stream map
Value stream mapping (VSM) documents material and information flow, identifying waste and non-value-added steps.
Question 3: In a 2-level full factorial DOE, an interaction effect between factors A and B means:
- A and B are correlated in the data collection phase
- The effect of A on Y depends on the level of B (Correct answer)
- Both A and B are statistically significant main effects
- A and B must be controlled at the same level
Correct answer: The effect of A on Y depends on the level of B
An interaction means the combined effect of A and B on the response is not simply additive—the level of one factor changes the effect of the other.
Question 4: A Black Belt calculates the p-value for a hypothesis test as 0.03 with α = 0.05. The correct conclusion is:
- Fail to reject H₀ because p > 0.01
- Reject H₀ because p < α (Correct answer)
- Accept H₁ as proven true
- The result is inconclusive
Correct answer: Reject H₀ because p < α
Since p-value (0.03) < α (0.05), there is sufficient evidence to reject the null hypothesis.
Question 5: The primary purpose of a SIPOC diagram in the Define phase is to:
- Identify root causes of defects
- Provide a high-level view of the process scope and stakeholders (Correct answer)
- Establish statistical control limits
- Prioritize improvement actions
Correct answer: Provide a high-level view of the process scope and stakeholders
SIPOC maps Suppliers, Inputs, Process steps, Outputs, and Customers to define process boundaries at a macro level.
Question 6: Takt time is calculated as:
- Total production time divided by customer demand rate (Correct answer)
- Cycle time minus waste time
- Number of defects divided by opportunities
- Available capacity divided by resource cost
Correct answer: Total production time divided by customer demand rate
Takt time = available production time ÷ customer demand, setting the production pace to match demand.
Question 7: When a Black Belt applies the Box-Cox transformation to process data, the primary objective is to:
- Remove outliers from the dataset
- Transform non-normal data to approximate normality for parametric analysis (Correct answer)
- Calculate the process Sigma level
- Identify special cause variation
Correct answer: Transform non-normal data to approximate normality for parametric analysis
The Box-Cox transformation applies a power transformation to stabilize variance and normalize non-normal data.
Certified Six Sigma Black Belt Exam Practice 4
A process is in statistical control but producing 15% defects.
The appropriate response is to: