Lean Six Sigma Green Belt Certification Analyze Phase Tools 3 — Questions and Answers
Question 1: A process has Cp = 1.5 but Cpk = 0.9. What does this combination indicate?
- The process spread is too wide for the specification
- The process is centered but has high variability
- The process has adequate spread but is off-center relative to specification (Correct answer)
- Both spread and centering are acceptable
Correct answer: The process has adequate spread but is off-center relative to specification
When Cp exceeds Cpk, the process spread fits within specs but the process mean is shifted away from the target.
Question 2: Which tool is most appropriate for visually separating the distribution of a continuous output variable across three or more categorical input groups?
- Run chart
- Box plot (Correct answer)
- Pareto chart
- Histogram
Correct answer: Box plot
Box plots side-by-side allow quick visual comparison of median, spread, and outliers across multiple groups.
Question 3: A team is analyzing warranty data coded as 'Pass' or 'Fail' against two suppliers (A and B). Which statistical test is most appropriate?
- Two-sample t-test
- One-way ANOVA
- Chi-square test of independence (Correct answer)
- F-test
Correct answer: Chi-square test of independence
A chi-square test of independence evaluates whether two categorical variables (supplier and pass/fail) are related.
Question 4: What is the purpose of the 'Is/Is Not' analysis tool in the Analyze phase?
- To calculate the probability of defect occurrence
- To narrow down potential root causes by defining where the problem does and does not occur (Correct answer)
- To map the process flow and identify non-value-added steps
- To quantify the financial impact of each potential cause
Correct answer: To narrow down potential root causes by defining where the problem does and does not occur
Is/Is Not analysis systematically scopes the problem by identifying boundaries where the issue exists versus where it does not.
Question 5: In hypothesis testing, a p-value of 0.03 with α = 0.05 leads to which conclusion?
- Fail to reject the null hypothesis; no significant difference
- Reject the null hypothesis; the difference is statistically significant (Correct answer)
- The alternative hypothesis is proven true
- The test is inconclusive and more data are needed
Correct answer: Reject the null hypothesis; the difference is statistically significant
Since p (0.03) < α (0.05), there is sufficient evidence to reject the null hypothesis at the 5% significance level.
Question 6: A Green Belt uses a regression equation: Y = 12.4 + 3.2X. If X increases by 2 units, what is the predicted change in Y?
- 3.2 units
- 6.4 units (Correct answer)
- 12.4 units
- 18.8 units
Correct answer: 6.4 units
The slope (3.2) represents the change in Y per unit change in X, so a 2-unit increase gives 3.2 × 2 = 6.4.
Question 7: Which graphical tool is specifically designed to display the stability of a process over time using control limits?
- Histogram
- Scatter diagram
- Control chart (Correct answer)
- Pareto chart
Correct answer: Control chart
Control charts plot sequential data with statistically calculated upper and lower control limits to assess process stability.
Lean Six Sigma Green Belt Certification Analyze Phase Tools 3
A process has Cp = 1.5 but Cpk = 0.9.
What does this combination indicate?