Green Belt Practice Question Bank

Original practice questions by domain, each with a worked explanation. scripts/quiz.py reads this file: keep the ### <id> | <domain> heading, options - A)..- D), Answer: and Why: lines.

#F01 | Fundamentals

A process running at 3.4 defects per million opportunities is described as:

• A) 3 sigma
• B) 4.5 sigma short-term
• C) 6 sigma short-term (with the 1.5 sigma shift)
• D) 6 sigma long-term Answer: C Why: 3.4 DPMO is the long-term tail at 4.5 sigma; adding the conventional 1.5 shift gives 6 sigma short-term.

#F02 | Fundamentals

Producing more, or earlier, than the next process or customer needs is which waste?

• A) Inventory
• B) Overproduction
• C) Motion
• D) Over-processing Answer: B Why: Overproduction is making too much or too early; it creates inventory, which is a separate waste.

#F03 | Fundamentals

Available time is 27,000 s per shift and customer demand is 450 units per shift. What is the takt time?

• A) 45 s
• B) 60 s
• C) 75 s
• D) 600 s Answer: B Why: Takt = available time / demand = 27,000 / 450 = 60 s per unit.

#F04 | Fundamentals

Which role sponsors a project, selects it and removes organisational barriers?

• A) Champion
• B) Green belt
• C) Process owner
• D) Master black belt Answer: A Why: The champion (sponsor) owns the business case and removes barriers; the process owner sustains the gains.

#F05 | Fundamentals

Three steps have first-pass yields of 95%, 90% and 98%. What is the rolled throughput yield?

• A) 90.8%
• B) 83.8%
• C) 94.3%
• D) 98.0% Answer: B Why: RTY = 0.95 x 0.90 x 0.98 = 0.838. The average (94.3%) hides the hidden factory.

#F06 | Fundamentals

In the Kano model, a feature whose absence causes dissatisfaction but whose presence does not raise satisfaction is:

• A) Must-be (basic)
• B) Performance (one-dimensional)
• C) Attractive (delighter)
• D) Indifferent Answer: A Why: Basic requirements are expected; meeting them only avoids dissatisfaction.

#D01 | Define

A good problem statement contains:

• A) The root cause
• B) The proposed solution
• C) What, where, when and the magnitude of the gap
• D) The names of the team members Answer: C Why: The problem statement describes the measurable gap; causes come in Analyze and solutions in Improve.

#D02 | Define

In a SIPOC diagram, the "C" stands for:

• A) Controls
• B) Customers
• C) Costs
• D) CTQs Answer: B Why: Suppliers, Inputs, Process, Outputs, Customers.

#D03 | Define

A customer need translated into a measurable requirement with a specification is a:

• A) CTQ
• B) SIPOC
• C) RACI
• D) Gantt chart Answer: A Why: Critical-to-quality characteristics come from the voice of the customer via a CTQ tree.

#D04 | Define

Which tool is used to agree what is inside and outside the project scope?

• A) In-frame / out-of-frame
• B) Pareto chart
• C) Control chart
• D) Scatter plot Answer: A Why: In/out of frame (or scope statements) makes boundaries explicit before the project starts.

#D05 | Define

Which of these is a cost of poor quality?

• A) The annual training budget
• B) Scrap, rework and warranty claims
• C) Machine depreciation
• D) Design engineers' salaries Answer: B Why: COPQ covers internal failure (scrap, rework), external failure (warranty, returns) and appraisal.

#D06 | Define

An operational definition of the primary metric is needed so that:

• A) Everyone measures and counts it the same way
• B) The metric improves faster
• C) The project can skip Measure
• D) The champion can approve the charter Answer: A Why: Without an operational definition, different people produce different numbers for the same process.

#M01 | Measure

A Gage R&R study gives 25% of study variation and ndc = 6. The measurement system is:

• A) Acceptable
• B) Conditionally acceptable
• C) Unacceptable
• D) Impossible to judge Answer: B Why: Under 10% is acceptable, 10-30% conditionally acceptable depending on the application, over 30% unacceptable; ndc >= 5 is met.

#M02 | Measure

The minimum recommended number of distinct categories (ndc) for a gauge used for process control is:

• A) 2
• B) 3
• C) 5
• D) 10 Answer: C Why: AIAG recommends ndc of 5 or more.

#M03 | Measure

USL = 10.6, LSL = 9.4 and sigma = 0.1. What is Cp?

• A) 1.00
• B) 1.33
• C) 2.00
• D) 4.00 Answer: C Why: Cp = (USL - LSL) / 6 sigma = 1.2 / 0.6 = 2.0.

#M04 | Measure

Same process: USL 10.6, LSL 9.4, sigma 0.1, mean 10.2. What is Cpk?

• A) 1.33
• B) 2.00
• C) 2.67
• D) 0.67 Answer: A Why: Cpk = min((10.6 - 10.2) / 0.3, (10.2 - 9.4) / 0.3) = min(1.33, 2.67) = 1.33.

#M05 | Measure

"Number of scratches per panel" is what type of data?

• A) Continuous
• B) Count (discrete)
• C) Ordinal
• D) Nominal Answer: B Why: Counts of defects per unit are discrete; they are charted with c or u charts.

#M06 | Measure

Subgroups of 5 give R-bar = 0.4652 (d2 = 2.326). What is the within-subgroup sigma estimate?

• A) 0.093
• B) 0.200
• C) 0.465
• D) 1.082 Answer: B Why: sigma = R-bar / d2 = 0.4652 / 2.326 = 0.200.

#A01 | Analyze

To compare mean tensile strength from three suppliers (normal data), use:

• A) Chi-square test
• B) One-way ANOVA
• C) Paired t-test
• D) 2-proportion test Answer: B Why: A continuous Y across three or more groups is compared with one-way ANOVA.

#A02 | Analyze

A test gives p = 0.03 with alpha = 0.05. The correct conclusion is:

• A) Fail to reject H0
• B) Reject H0
• C) Accept H0
• D) H1 is proven false Answer: B Why: p < alpha, so reject the null hypothesis; we never "accept" H0.

#A03 | Analyze

A type II error is:

• A) Rejecting a true null hypothesis
• B) Failing to reject a false null hypothesis
• C) The same as alpha
• D) Using the wrong test Answer: B Why: Beta (type II) is missing a real difference; alpha (type I) is a false alarm.

#A04 | Analyze

A correlation coefficient r = -0.9 means:

• A) A weak negative relationship
• B) A strong negative linear relationship
• C) X causes Y to fall
• D) No relationship Answer: B Why: |r| close to 1 is a strong linear relationship; correlation does not prove causation.

#A05 | Analyze

A simple regression has R-sq = 0.64 and a positive slope. What is r?

• A) 0.41
• B) 0.64
• C) 0.80
• D) 0.32 Answer: C Why: For simple linear regression r = sqrt(R-sq) = 0.8, with the sign of the slope.

#A06 | Analyze

To compare the defective rates (pass/fail) of two shifts, use:

• A) 2-sample t-test
• B) 2-proportion test
• C) One-way ANOVA
• D) F-test Answer: B Why: The output is attribute (proportion defective) and there are two groups.

#I01 | Improve

How many runs does a 2^(5-1) fractional factorial design have (no replicates, no centre points)?

• A) 8
• B) 16
• C) 32
• D) 10 Answer: B Why: 2^(5-1) = 2^4 = 16 runs.

#I02 | Improve

In a resolution IV design:

• A) Main effects are aliased with two-factor interactions
• B) Main effects are clear of two-factor interactions, which are aliased with each other
• C) All main effects and two-factor interactions are clear
• D) There is no aliasing Answer: B Why: Resolution IV: shortest word in the defining relation has 4 letters.

#I03 | Improve

The response averages 52 at the high level of factor A and 46 at the low level. The effect of A is:

• A) 3
• B) 6
• C) 49
• D) 98 Answer: B Why: Effect = mean(high) - mean(low) = 6; the coded regression coefficient is half of it (3).

#I04 | Improve

Poka-yoke means:

• A) Mistake-proofing
• B) 5S
• C) Visual management
• D) Kanban Answer: A Why: Poka-yoke devices prevent or immediately detect errors.

#I05 | Improve

Why is the run order of an experiment randomised?

• A) To reduce the number of runs
• B) To protect against lurking variables and time trends
• C) To increase the resolution
• D) To remove interactions Answer: B Why: Randomisation spreads unknown time-related effects across all factor settings.

#I06 | Improve

Centre points added to a two-level factorial allow you to detect:

• A) Interactions
• B) Curvature
• C) Aliasing
• D) Blocks Answer: B Why: Comparing the centre mean with the factorial mean tests for curvature (and gives pure error).

#C01 | Control

X-double-bar = 50, R-bar = 4, n = 5 (A2 = 0.577). What is the UCL of the X-bar chart?

• A) 52.31
• B) 54.00
• C) 51.15
• D) 56.92 Answer: A Why: UCL = 50 + 0.577 x 4 = 52.31.

#C02 | Control

Which chart is used for fraction defective with a varying sample size?

• A) np chart
• B) p chart
• C) c chart
• D) u chart Answer: B Why: p charts plot the fraction defective and allow limits to vary with n.

#C03 | Control

Eight consecutive points on one side of the centre line most likely indicate:

• A) Normal variation
• B) A shift in the process mean
• C) Increased variation only
• D) Over-control Answer: B Why: A run of 8 (Western Electric rule 4) signals a sustained shift.

#C04 | Control

When an out-of-specification part is found, the reaction plan should first:

• A) Adjust the machine and continue
• B) Stop, contain suspect product since the last good check, then correct
• C) Recalculate the control limits
• D) Increase the sample size next week Answer: B Why: Containment protects the customer; correction follows.

#C05 | Control

Control limits are calculated from:

• A) The specification limits
• B) Process data
• C) The customer's requirements
• D) The engineering drawing Answer: B Why: Control limits describe the voice of the process; specifications are the voice of the customer.

#C06 | Control

At the end of the Control phase, ownership of the improved process is handed to the:

• A) Champion
• B) Process owner
• C) Master black belt
• D) Finance team Answer: B Why: The process owner keeps the control plan alive; finance only validates savings.