Six Sigma Green Belt Practice Test
Six Sigma Green Belt Control Phase Practice Questions
Control Phase makes up 7 of every 50 questions on a Tigertest Six Sigma Green Belt practice test. Here are 10 of the 28 questions on it, each with the answer and the reason.
Updated by the Tigertest team. Based on the ASQ CSSGB Body of Knowledge (2022). Original questions; 50 per test, weighted like the real exam, with a 70% readiness line. Not affiliated with ASQ.
1. What is the main objective of statistical process control?
- A.To remove all variation
- B.To detect special causes early
- C.To sort good parts from bad
- D.To set the specification limits
Answer: B. SPC monitors a process over time so special cause variation is spotted and acted on before it produces defects. Some common cause variation always remains.
2. Which describes common cause variation?
- A.A new untrained operator
- B.A bad batch of material
- C.A sudden tool breakage
- D.Built-in process noise
Answer: D. Common causes are the many small sources always present in a stable process. Reducing them needs a change to the process itself, usually by management.
3. A point falls outside the upper control limit after a material change. What does this most likely signal?
- A.A special cause
- B.A specification change
- C.Common cause noise
- D.A need for wider limits
Answer: A. A point beyond a 3 sigma limit is unlikely from common causes alone, so the team looks for an assignable cause, here probably the new material.
4. An operator adjusts the machine after every point that is not exactly on target. What is the likely result?
- A.A perfectly centered process
- B.No change in variation
- C.More variation, not less
- D.Less variation over time
Answer: C. Adjusting a stable process in response to common cause noise is tampering (over-adjustment), which Deming's funnel experiment shows increases variation.
5. Which pattern on a control chart signals a special cause even though every point is inside the limits?
- A.About two thirds within one sigma
- B.No points beyond the limits
- C.Six points in a row steadily rising
- D.Points spread randomly about the center
Answer: C. Run rules flag non-random patterns inside the limits, such as six points in a row steadily increasing or decreasing (a trend), a long run on one side of the center line, or repeated points near a limit.
6. What is the aim of rational subgrouping?
- A.Only common causes within subgroups
- B.Subgroups mix shifts on purpose
- C.Subgroups are as large as possible
- D.Every subgroup has equal means
Answer: A. Rational subgroups are chosen, often consecutive parts made close together in time, so that within-subgroup variation reflects only common causes and shifts appear between subgroups.
7. A team forms each subgroup from one part per shift over three shifts. What is the risk?
- A.No data can be used at all
- B.The chart cannot be drawn
- C.The limits become too narrow
- D.Range picks up shift effects
Answer: D. Mixing shifts inside a subgroup puts between-shift variation into the range, so the limits widen and real shift-to-shift changes go undetected.
8. Why are subgroups usually small, such as 4 or 5 consecutive parts?
- A.To fill the chart more quickly
- B.To capture short-term variation
- C.To save money on gauges
- D.To force the data to normal
Answer: B. Small subgroups taken close together keep within-subgroup variation to short-term common causes, which makes the chart sensitive to shifts between subgroups.
9. Which chart pair suits continuous data collected in subgroups of 5?
- A.Individuals and moving range
- B.X-bar and R
- C.p and np
- D.c and u
Answer: B. X-bar and R charts track the subgroup average and range for variable data in small subgroups. ImR is for one reading at a time.
10. Which chart pair is preferred for variable data in subgroups of 12 or more?
- A.Individuals and moving range
- B.np and p
- C.X-bar and R
- D.X-bar and s
Answer: D. With larger subgroups the standard deviation estimates spread more efficiently than the range, so X-bar and s charts are used.
Practice all 28 control phase questions, and the rest of the 200-question bank, in the free Six Sigma Green Belt training sets. Questions you miss come back until you have mastered them.
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