Lean Six Sigma Green Belt Certification Lean Six Sigma Green Belt Analyze Phase Tools 1 — Questions and Answers
Question 1: What is the primary purpose of a fishbone (Ishikawa) diagram in the Analyze phase?
- To display the frequency distribution of a single continuous variable
- To identify and organize potential root causes of a defect or problem (Correct answer)
- To measure the degree of linear correlation between two variables
- To determine whether a process output meets specification limits
Correct answer: To identify and organize potential root causes of a defect or problem
The fishbone diagram structures potential causes into categories (such as Man, Machine, Method, Material, Measurement, and Environment) so teams can systematically brainstorm and organize root causes rather than treating them as an unstructured list.
Question 2: In a one-way ANOVA, which statistical measure is being compared across the groups?
- The medians of each group
- The ranges of each group
- The standard deviations of each group
- The means of each group (Correct answer)
Correct answer: The means of each group
ANOVA (Analysis of Variance) tests whether the means of three or more groups are statistically equal by partitioning total variation into within-group and between-group components and comparing them via an F-ratio.
Question 3: What does the R-squared (R²) value indicate in a simple linear regression output?
- The slope of the best-fit regression line
- The p-value used to assess significance of the model
- The proportion of total variation in Y that is explained by X (Correct answer)
- The residual error for each individual data point
Correct answer: The proportion of total variation in Y that is explained by X
R-squared, or the coefficient of determination, quantifies how much of the variability in the response variable (Y) is accounted for by the predictor variable (X) in the regression model. A value of 1.0 means the model explains all variation.
Question 4: A multi-vari chart is primarily used in the Analyze phase to:
- Rank defect categories from most frequent to least frequent
- Display cumulative percentage of defects across process steps
- Identify and compare multiple families of variation (within-unit, unit-to-unit, time-to-time) (Correct answer)
- Calculate the process capability index for a critical characteristic
Correct answer: Identify and compare multiple families of variation (within-unit, unit-to-unit, time-to-time)
Multi-vari charts graphically reveal the dominant source of variation by displaying within-piece, piece-to-piece, and time-to-time variation simultaneously, allowing the team to focus detailed statistical analysis on the right family of variation.
Question 5: A process has a Cpk of 0.85. What does this indicate?
- The process is centered and fully capable of meeting specification limits
- The process is capable but slightly off-center within the specification limits
- The process is not capable of consistently producing output within specification limits (Correct answer)
- The process has negligible variation and exceeds all customer requirements
Correct answer: The process is not capable of consistently producing output within specification limits
A Cpk below 1.00 means the process is not capable — it will produce defects outside specification limits. A Cpk of at least 1.33 is typically required to demonstrate adequate short-term capability, and 1.67 or higher for critical characteristics.
Question 6: In the Analyze phase, a Pareto chart supports the team's work primarily by:
- Mapping the sequence of value-added and non-value-added steps in the process
- Plotting process output over time to detect trends and shifts
- Prioritizing the vital few defect categories that account for the majority of problems (Correct answer)
- Displaying the relationship between a continuous input and a continuous output
Correct answer: Prioritizing the vital few defect categories that account for the majority of problems
Based on the Pareto (80/20) principle, a Pareto chart ranks defect types or failure causes by frequency or cost, helping the team focus improvement resources on the small number of categories responsible for most of the harm rather than spreading effort uniformly.
Lean Six Sigma Green Belt Certification Lean Six Sigma Green Belt Analyze Phase Tools 1
What is the primary purpose of a fishbone (Ishikawa) diagram in the Analyze phase?