CLL Data Analysis & Reporting 3 — Questions and Answers
Question 1: A Lean leader wants to determine if a process improvement reduced average cycle time. Which statistical test is most appropriate when comparing before and after means from the same process?
- Chi-square test
- Paired t-test (Correct answer)
- ANOVA
- Regression analysis
Correct answer: Paired t-test
A paired t-test compares means from the same process at two time points, controlling for process-to-process variability.
Question 2: What does a negative correlation coefficient (r = -0.87) between defect rate and inspection frequency indicate?
- Inspection frequency has no effect on defects
- As inspection frequency increases, defect rate decreases (Correct answer)
- Both variables increase together
- The data contains outliers that must be removed
Correct answer: As inspection frequency increases, defect rate decreases
A negative r close to -1 indicates a strong inverse relationship: as one variable increases, the other decreases.
Question 3: In lean reporting, what is the difference between a lagging indicator and a leading indicator?
- Lagging indicators predict future performance; leading indicators confirm past results
- Leading indicators predict future performance; lagging indicators confirm past results (Correct answer)
- Both measure the same outcomes at different time intervals
- Leading indicators are financial; lagging indicators are operational
Correct answer: Leading indicators predict future performance; lagging indicators confirm past results
Leading indicators signal future outcomes (e.g., near-miss counts), while lagging indicators confirm what already happened (e.g., injury rate).
Question 4: A team is using a Pugh matrix to evaluate data collection methods. What is the primary function of this tool?
- Calculate process sigma level
- Rank and compare alternatives against criteria systematically (Correct answer)
- Map data flow through the value stream
- Identify root causes of data errors
Correct answer: Rank and compare alternatives against criteria systematically
A Pugh matrix evaluates multiple alternatives against weighted criteria using a structured scoring approach to support decision-making.
Question 5: Which of the following best describes the purpose of stratification in data analysis?
- Averaging data across all categories to find the overall trend
- Separating data into subgroups to identify patterns within categories (Correct answer)
- Removing outliers before calculating summary statistics
- Ranking defects by their cost impact
Correct answer: Separating data into subgroups to identify patterns within categories
Stratification splits data by categories such as shift, machine, or operator to reveal hidden sources of variation.
Question 6: A value stream map shows process data boxes under each step. Which metric does NOT typically appear in these data boxes?
- Cycle time
- Changeover time
- Uptime percentage
- Customer satisfaction score (Correct answer)
Correct answer: Customer satisfaction score
VSM data boxes capture operational metrics like cycle time, changeover, and uptime; customer satisfaction is a separate strategic measure.
Question 7: When plotting a run chart, how many consecutive data points on one side of the median constitutes a statistically significant run signal?
- 4
- 6
- 8 (Correct answer)
- 10
Correct answer: 8
Eight or more consecutive points on the same side of the median indicates a non-random run, signaling a process shift.
CLL Data Analysis & Reporting 3
A Lean leader wants to determine if a process improvement reduced average cycle time.
Which statistical test is most appropriate when comparing before and after means from the same process?