CPT Quality Practices & Measurement 3 — Questions and Answers
Question 1: What does a Cp value of 1.33 indicate about a process?
- The process is barely capable
- The process is not capable
- The process has good capability with a margin (Correct answer)
- The process is producing zero defects
Correct answer: The process has good capability with a margin
Cp of 1.33 means the process spread fits within the tolerance with roughly a 25% margin on each side, indicating good capability.
Question 2: Which of the following best describes 'measurement uncertainty'?
- The difference between two measurements of the same part
- A parameter that characterizes the dispersion of measured values (Correct answer)
- The calibration interval for a gauge
- The bias of a measuring instrument
Correct answer: A parameter that characterizes the dispersion of measured values
Measurement uncertainty is a quantified estimate of the range of values within which the true value likely falls.
Question 3: In a Pareto analysis of defects, which defects should be addressed first?
- The most recently occurring defects
- The defects with the highest frequency or cost (Correct answer)
- The defects easiest to fix
- The defects reported by customers
Correct answer: The defects with the highest frequency or cost
Pareto analysis follows the 80/20 rule — addressing the vital few defects with highest frequency or cost yields the greatest quality improvement.
Question 4: What is 'gage repeatability' in a Gage R&R study?
- Variation between different operators using the same gage
- Variation when the same operator measures the same part multiple times (Correct answer)
- Variation caused by part-to-part differences
- The accuracy of the gage compared to a standard
Correct answer: Variation when the same operator measures the same part multiple times
Repeatability measures the gage's inherent variation when one operator repeatedly measures the same part under the same conditions.
Question 5: Which SPC rule indicates a potential process shift when 9 consecutive points fall on one side of the centerline?
- Rule 1 – One point beyond 3σ
- Rule 2 – Nine points in a row on one side (Correct answer)
- Rule 3 – Six points trending in one direction
- Rule 4 – Fourteen alternating points
Correct answer: Rule 2 – Nine points in a row on one side
The Nelson/Western Electric rule identifying 9 consecutive points on one side of the centerline signals a likely process mean shift.
Question 6: A dimension is specified as 2.500 ± 0.010 inches. What is the total tolerance band?
- 0.005 inch
- 0.010 inch
- 0.020 inch (Correct answer)
- 0.025 inch
Correct answer: 0.020 inch
The total tolerance band is the sum of the upper and lower deviations: 0.010 + 0.010 = 0.020 inch.
Question 7: Which tool is used to measure the inside diameter of a bore with high precision?
- Outside micrometer
- Vernier caliper
- Bore gauge (telescoping gauge + micrometer) (Correct answer)
- Dial indicator on a surface plate
Correct answer: Bore gauge (telescoping gauge + micrometer)
A bore gauge (or telescoping gauge transferred to a micrometer) is the standard method for accurately measuring internal diameters.
CPT Quality Practices & Measurement 3
What does a Cp value of 1.33 indicate about a process?