ASQ Six Sigma Green Belt 4 — Questions and Answers
Question 1: A Green Belt wants to test whether there is a significant difference in mean cycle times between three machine types. Which statistical test is most appropriate?
- Two-sample t-test
- Chi-square test
- One-way ANOVA (Correct answer)
- Paired t-test
Correct answer: One-way ANOVA
One-way ANOVA compares means across three or more groups simultaneously, making it appropriate for comparing cycle times among three machine types.
Question 2: What is the purpose of a process capability index (Ppk) as distinct from Cpk?
- Ppk uses within-subgroup variation while Cpk uses overall variation
- Ppk uses overall process variation while Cpk uses within-subgroup short-term variation (Correct answer)
- Ppk is used for attribute data while Cpk is used for variable data
- Ppk measures centering while Cpk measures spread
Correct answer: Ppk uses overall process variation while Cpk uses within-subgroup short-term variation
Ppk uses total (long-term) standard deviation including all sources of variation, while Cpk uses within-subgroup (short-term) variation representing process entitlement.
Question 3: In a control chart, what does an 'out-of-control' signal indicate?
- The process has produced a defective unit
- A special cause of variation is likely present (Correct answer)
- The process mean has shifted permanently
- The specification limits have been exceeded
Correct answer: A special cause of variation is likely present
An out-of-control signal on a control chart indicates a statistically unusual pattern suggesting a special (assignable) cause of variation is present.
Question 4: Which lean tool is used to visually map the flow of materials and information to identify waste and non-value-added activities?
- 5S methodology
- Value Stream Mapping (VSM) (Correct answer)
- Kanban system
- Heijunka (production leveling)
Correct answer: Value Stream Mapping (VSM)
Value Stream Mapping creates a visual representation of the entire process flow, highlighting waste, delays, and non-value-added steps that are candidates for elimination.
Question 5: A team applies the 5 Whys technique. What is the main risk of this analysis method?
- It requires advanced statistical software to implement
- It can lead to different root causes depending on who is asking the questions (Correct answer)
- It only works for manufacturing processes, not service processes
- It cannot identify more than one root cause per problem
Correct answer: It can lead to different root causes depending on who is asking the questions
The 5 Whys is vulnerable to subjective bias since different teams may trace different causal chains from the same symptom, potentially reaching different root causes.
Question 6: What does 'measurement system bias' mean in the context of a Gage R&R study?
- The measurement system produces inconsistent results between operators
- The measurement system consistently reads higher or lower than the true value (Correct answer)
- The measurement device varies in precision across its measurement range
- The repeatability of the gage is poor under controlled conditions
Correct answer: The measurement system consistently reads higher or lower than the true value
Bias is a systematic offset between the measurement system's average reading and the true reference value, indicating a calibration issue.
Question 7: In the Control phase, which document defines the actions to take if a process goes out of control?
- Project charter
- Control plan (Correct answer)
- FMEA
- Measurement system analysis report
Correct answer: Control plan
The control plan specifies monitoring methods, control limits, response plans, and responsible parties for sustaining process improvements.
ASQ Six Sigma Green Belt 4
A Green Belt wants to test whether there is a significant difference in mean cycle times between three machine types.
Which statistical test is most appropriate?