Lean Six Sigma Green Belt Certification DMAIC: Analyze Phase Techniques 2 — Questions and Answers
Question 1: A Green Belt notices that a process produces more defects on Monday mornings than other times. Which stratification analysis should be performed first?
- Regression analysis by operator
- Time-based stratification by shift and day (Correct answer)
- Pareto chart of defect types only
- Control chart with no stratification
Correct answer: Time-based stratification by shift and day
Time-based stratification breaks data into segments (shift, day, week) to reveal patterns linked to specific conditions like Monday morning starts.
Question 2: In hypothesis testing for a Green Belt project, a p-value of 0.03 is obtained with α = 0.05. What is the correct conclusion?
- Fail to reject the null hypothesis
- Reject the null hypothesis (Correct answer)
- The result is inconclusive
- Increase the sample size and retest
Correct answer: Reject the null hypothesis
Since p-value (0.03) < α (0.05), there is sufficient evidence to reject the null hypothesis.
Question 3: Which tool is BEST used to quantify the relationship strength between a continuous X variable and a continuous Y variable during the Analyze phase?
- Pearson correlation coefficient (Correct answer)
- Chi-square test
- Mood's median test
- Attribute agreement analysis
Correct answer: Pearson correlation coefficient
Pearson correlation coefficient measures the strength and direction of a linear relationship between two continuous variables.
Question 4: A team uses a multi-vari chart and finds that variation is greatest between different machines compared to within-machine or time-based variation. This indicates which type of variation source?
- Positional variation (Correct answer)
- Cyclical variation
- Temporal variation
- Unit-to-unit variation
Correct answer: Positional variation
Variation between different machines (or positions/fixtures) is classified as positional variation in a multi-vari study.
Question 5: During the Analyze phase, a team wants to determine whether training (yes/no) affects defect rate (defective/not defective). Which statistical test is most appropriate?
- Two-sample t-test
- ANOVA
- Chi-square test of independence (Correct answer)
- Simple linear regression
Correct answer: Chi-square test of independence
Chi-square test of independence is used when both the input and output variables are categorical (attribute data).
Question 6: What does a steep slope on a Pareto chart's cumulative percentage line early in the chart indicate?
- All defect categories contribute equally
- A few categories account for the majority of defects (Correct answer)
- The data is normally distributed
- Measurement system error is high
Correct answer: A few categories account for the majority of defects
A steep early cumulative line confirms the 80/20 principle — a few categories drive most of the defects.
Question 7: In regression analysis, a coefficient of determination (R²) of 0.85 means:
- 85% of the data points fall within the confidence interval
- The model has an 85% chance of being correct
- 85% of the variation in Y is explained by the X variable(s) in the model (Correct answer)
- The correlation coefficient is 0.85
Correct answer: 85% of the variation in Y is explained by the X variable(s) in the model
R² represents the proportion of variance in the response variable (Y) that is explained by the predictor variable(s) in the regression model.
Lean Six Sigma Green Belt Certification DMAIC: Analyze Phase Techniques 2
A Green Belt notices that a process produces more defects on Monday mornings than other times.
Which stratification analysis should be performed first?