IASSC Lean Six Sigma Green Belt Practice Test

IASSC Lean Six Sigma Green Belt is a DMAIC-centered route for candidates who support or lead improvement work using process data, root-cause analysis, improvement selection, and control planning.

What Green Belt practice should test

• matching DMAIC phase to the right tool or decision
• interpreting measurement, analysis, root-cause, improvement, and control scenarios
• recognizing when process data supports action and when more measurement is needed
• choosing practical improvement controls rather than one-time fixes

Sample Exam Questions

Try these 12 original IASSC Lean Six Sigma Green Belt sample questions for self-assessment. They are written for practice and route-fit review; they are not official IASSC exam questions.

Question 1

Topic: project charter

A Green Belt project has a broad goal to “improve customer onboarding.” Which charter improvement is most useful?

• A. Remove the business case so the team can start faster
• B. Add a clear problem statement, scope, goal, timeline, stakeholders, and expected benefit
• C. List every possible solution before measurement
• D. Assign no process owner until Control

Best answer: B

Explanation: A project charter aligns the team on the problem, scope, goal, benefits, stakeholders, and timing. Green Belt questions often test whether a project is defined clearly enough to proceed.

Question 2

Topic: measurement plan

A team wants to compare defect rates across shifts, but each shift currently defines a defect differently. What should happen first?

• A. Average the results anyway
• B. Pick the shift with the lowest defect rate
• C. Skip measurement and move to Improve
• D. Standardize operational definitions and data-collection rules

Best answer: D

Explanation: Measurement is unreliable if teams define defects differently. A Green Belt must establish consistent operational definitions before comparing data.

Question 3

Topic: process baseline

Before selecting solutions, the team needs to understand current performance. Which action best supports this?

• A. Collect baseline data on the process measure and confirm how it is calculated
• B. Choose a solution based on the loudest complaint
• C. Redesign the process without a current-state view
• D. Close the project after one anecdote

Best answer: A

Explanation: Baseline measurement lets the team understand current performance and later evaluate improvement. Without a baseline, improvement claims are weak.

Question 4

Topic: root cause analysis

A cause-and-effect session produces many possible causes for late deliveries. What should the team do next?

• A. Treat every idea as proven
• B. Select the easiest idea to fix without evidence
• C. Prioritize likely causes and verify them with data or process evidence
• D. Stop the project because there are too many ideas

Best answer: C

Explanation: Brainstormed causes are hypotheses, not proof. Green Belt analysis requires prioritizing and verifying causes before improvement selection.

Question 5

Topic: data interpretation

A weekly chart shows common ups and downs but no clear shift after a process change. What is the best interpretation?

• A. The process has definitely improved
• B. The chart proves the customer is wrong
• C. The team should ignore all future data
• D. The evidence may not support a real process change yet

Best answer: D

Explanation: Green Belt candidates should avoid overclaiming from noise. If the data does not show a meaningful shift or pattern, more evidence or a different improvement may be needed.

Question 6

Topic: improvement selection

Two solutions are proposed. One is cheap and addresses a verified root cause; the other is expensive and unrelated to the measured problem. Which is the better Green Belt decision?

• A. Choose the expensive solution because it looks more impressive
• B. Choose the solution tied to the verified root cause and expected impact
• C. Choose both without testing
• D. Delay all decisions until the project expires

Best answer: B

Explanation: Improvement selection should connect to verified causes, expected benefit, feasibility, and risk. Expensive or visible solutions are not automatically better.

Question 7

Topic: pilot testing

A process change may reduce rework but could slow throughput. What is the best next step before full rollout?

• A. Pilot the change, measure both rework and throughput, and adjust based on evidence
• B. Roll it out everywhere without measurement
• C. Ignore throughput because only rework matters
• D. Cancel the project because every change has risk

Best answer: A

Explanation: Pilots help teams test benefits and unintended effects before scaling. Green Belt decisions should balance multiple process measures when the scenario indicates tradeoffs.

Question 8

Topic: control planning

An improvement works during the project but depends on one supervisor reminding everyone daily. What is the main risk?

• A. The process will automatically improve forever
• B. The project has too many stakeholders
• C. The improvement may not be sustainable without standard work, ownership, and monitoring
• D. The team has too much data

Best answer: C

Explanation: Sustainable control should not rely only on memory or heroic supervision. The control plan should define ownership, standard work, measures, and response actions.

Question 9

Topic: stakeholder communication

A change affects customer service and operations, but only operations has been involved in testing. What should the Green Belt do?

• A. Ignore customer service because they are downstream
• B. Launch the change and let customer service adapt later
• C. Remove customer service from the process map
• D. Involve affected stakeholders before rollout to identify risks and adoption needs

Best answer: D

Explanation: Improvement projects can fail when impacted groups are excluded. Stakeholder involvement helps reveal handoff risks, training needs, and adoption barriers.

Question 10

Topic: control response

A control chart or monitoring plan shows performance drifting back toward the old level. What is the best response?

• A. Hide the chart until performance improves
• B. Follow the control plan, investigate causes, and take corrective action
• C. Declare the original project invalid without investigation
• D. Change the goal to match the drift

Best answer: B

Explanation: Control plans should define what to do when performance drifts. The response is to investigate and correct, not hide or redefine the problem.

Question 11

Topic: DMAIC phase matching

The team is confirming that the improved process is stable and assigning ongoing ownership. Which DMAIC phase is this?

• A. Control
• B. Define
• C. Measure
• D. Analyze

Best answer: A

Explanation: Control focuses on sustaining gains, monitoring performance, and transferring ownership to the process owner. It is different from initial measurement or root-cause analysis.

Question 12

Topic: Green Belt scope

Which behavior best reflects Green Belt-level practice?

• A. Jumping to preferred solutions before measuring the current process
• B. Treating every project as a statistical modeling exercise
• C. Leading or supporting DMAIC work with data, verified causes, practical improvements, and control planning
• D. Avoiding stakeholder communication until after implementation

Best answer: C

Explanation: Green Belt work is practical DMAIC execution. It blends process knowledge, data, root-cause thinking, improvement selection, stakeholder engagement, and control.

Green Belt quick checklist

• Do not compare data until operational definitions and collection rules are consistent.
• Treat root causes as hypotheses until verified with evidence.
• Pilot improvements when risk, throughput, customer impact, or handoffs could change.
• Build controls that survive after the project team leaves.

Related IASSC pages

• Yellow Belt
• Black Belt
• IASSC certification updates