Certified Six Sigma Black Belt Exam Practice 3 — Questions and Answers
Question 1: A gauge R&R study reveals that measurement variation accounts for 35% of total observed variation. What is the appropriate action?
- Accept the measurement system as adequate
- Improve or replace the measurement system before proceeding (Correct answer)
- Proceed but document the limitation
- Recalibrate once and retest
Correct answer: Improve or replace the measurement system before proceeding
A gauge R&R above 30% indicates an unacceptable measurement system that should be improved before drawing process conclusions.
Question 2: In the context of the transfer function Y = f(X), the Black Belt's primary goal during the Analyze phase is to:
- Establish the project charter
- Identify and validate the key X's driving Y (Correct answer)
- Implement controls on all X's
- Collect baseline data on Y
Correct answer: Identify and validate the key X's driving Y
The Analyze phase identifies and confirms which input variables (X's) significantly influence the output (Y).
Question 3: A team uses a correlation coefficient of r = -0.92. This indicates:
- A weak positive relationship
- A strong positive relationship
- A strong negative relationship (Correct answer)
- No meaningful relationship
Correct answer: A strong negative relationship
An r value close to -1 indicates a strong negative linear relationship between the two variables.
Question 4: Which statistical test is appropriate to determine if a process proportion defective has changed after an improvement?
- F-test
- 1-proportion z-test (Correct answer)
- Chi-square goodness of fit
- Mann-Whitney test
Correct answer: 1-proportion z-test
The 1-proportion z-test (or 2-proportion test) compares a sample proportion to a target or baseline proportion.
Question 5: A Black Belt wants to quantify how much a process output shifts for each unit change in a controlled input. Which analysis provides this directly?
- Simple linear regression (Correct answer)
- Hypothesis testing
- Control chart analysis
- Process capability study
Correct answer: Simple linear regression
Simple linear regression provides the slope coefficient, which quantifies the change in Y per unit change in X.
Question 6: The purpose of randomization in a designed experiment is to:
- Reduce the number of experimental runs needed
- Eliminate all sources of variation
- Guard against the effect of lurking variables and time-related trends (Correct answer)
- Ensure equal sample sizes across factor levels
Correct answer: Guard against the effect of lurking variables and time-related trends
Randomizing run order distributes the effects of uncontrolled nuisance variables evenly, preventing bias.
Question 7: Which type of failure mode severity rating (per FMEA scale) would apply to a failure that causes injury to an end user?
- 3–4
- 5–6
- 7–8
- 9–10 (Correct answer)
Correct answer: 9–10
In FMEA, severity ratings of 9–10 are reserved for failures that affect safety or regulatory compliance and may injure users.
Certified Six Sigma Black Belt Exam Practice 3
A gauge R&R study reveals that measurement variation accounts for 35% of total observed variation.
What is the appropriate action?