SPC Process Variation & Capability 1 — Questions and Answers
Question 1: What is the primary source of common cause variation?
- Operator error
- Machine failure
- Normal process variability (Correct answer)
- Incorrect specifications
Correct answer: Normal process variability
Common cause variation is inherent to the process and results from normal, random factors.
Question 2: What does a Cp value greater than 1.33 typically indicate?
- Out-of-control process
- High process capability (Correct answer)
- Excessive rework
- Poor tool calibration
Correct answer: High process capability
A Cp value above 1.33 suggests the process is capable of meeting specifications with minimal variation.
Question 3: Which tool is used to determine the spread and centering of a process?
- Fishbone diagram
- Pareto chart
- Capability histogram (Correct answer)
- Flowchart
Correct answer: Capability histogram
A capability histogram displays the process spread relative to specification limits, showing capability and centering.
Question 4: What does Cpk take into account that Cp does not?
- Sample size
- Process centering (Correct answer)
- Number of operators
- Total cost
Correct answer: Process centering
Cpk measures process capability while considering how centered the process is between the specification limits.
Question 5: Which term describes a process that consistently produces within specification limits?
- Corrective
- Capable (Correct answer)
- Variable
- Reactive
Correct answer: Capable
A capable process produces outputs within specification limits, reflecting good performance and low variation.
Question 6: What does a wide process spread compared to specification limits indicate?
- High precision
- Stable process
- Low process capability (Correct answer)
- Normal variation
Correct answer: Low process capability
If process spread exceeds the specification range, the process is likely incapable of consistently meeting quality targets.
SPC Process Variation & Capability 1
What is the primary source of common cause variation?