Certified Six Sigma Black Belt Exam Basic 4 — Questions and Answers
Question 1: Which chart is most appropriate for monitoring the proportion of defective items in a process with variable subgroup sizes?
- p-chart (Correct answer)
- c-chart
- X-bar and R chart
- np-chart
Correct answer: p-chart
The p-chart monitors the proportion of nonconforming items and accommodates variable subgroup sizes, unlike the np-chart which requires constant subgroup size.
Question 2: The concept of 'transfer function' in Six Sigma (Y = f(X)) means:
- Customer requirements transfer to engineering specifications
- Output quality is a function of input and process variables (Correct answer)
- Knowledge transfers from Black Belts to Green Belts
- Defects transfer between process steps
Correct answer: Output quality is a function of input and process variables
The transfer function Y = f(X) expresses that process outputs (Y) are determined by input variables and process factors (Xs), guiding teams to control the inputs to improve the output.
Question 3: What is the purpose of a Measurement System Analysis (MSA) before collecting process data?
- To confirm that operators are following standard work
- To ensure the measurement system's variation is acceptable relative to total variation (Correct answer)
- To determine which control chart type to use
- To calculate the sigma level of the measurement device
Correct answer: To ensure the measurement system's variation is acceptable relative to total variation
MSA verifies that measurement system variation is small enough relative to process variation and tolerances so that collected data accurately reflects the true process.
Question 4: In Design of Experiments (DOE), a 'full factorial' design means:
- Only the most significant factors are tested
- All possible combinations of factor levels are tested (Correct answer)
- Factors are tested one at a time while others are held constant
- A fractional subset of factor combinations is tested
Correct answer: All possible combinations of factor levels are tested
A full factorial design tests every combination of all factor levels, allowing estimation of all main effects and all interactions.
Question 5: What does 'Cpk' measure that 'Cp' does not?
- The width of the specification limits
- The actual process centering relative to the nearest specification limit (Correct answer)
- The long-term process performance over multiple shifts
- The number of defects produced per unit
Correct answer: The actual process centering relative to the nearest specification limit
Cpk adjusts for process centering by measuring the distance from the process mean to the nearest specification limit, penalizing off-centered processes unlike Cp.
Question 6: Which lean concept focuses on eliminating the 'waiting' waste by ensuring each process step is ready when the previous step completes?
- Poka-yoke
- Just-in-Time (JIT) (Correct answer)
- 5S methodology
- Kaizen
Correct answer: Just-in-Time (JIT)
Just-in-Time (JIT) aims to produce and deliver the right items at the right time in the right quantity, eliminating waiting and inventory waste.
Question 7: A scatter diagram showing a positive correlation between two variables indicates:
- One variable causes the other to increase
- As one variable increases, the other tends to increase as well (Correct answer)
- The variables are unrelated
- Both variables are controlled by the same factor
Correct answer: As one variable increases, the other tends to increase as well
A positive correlation means the two variables tend to increase together, but correlation does not imply causation without further analysis.
Certified Six Sigma Black Belt Exam Basic 4
Which chart is most appropriate for monitoring the proportion of defective items in a process with variable subgroup sizes?