CQE Inspection and Testing Methods 2 — Questions and Answers
Question 1: What is 'destructive testing' and when is it typically used?
- Testing that damages the test equipment
- Testing that renders the tested specimen unusable, typically used to determine material properties or failure modes (Correct answer)
- Testing performed on scrapped parts only
- Testing that exceeds regulatory safety limits
Correct answer: Testing that renders the tested specimen unusable, typically used to determine material properties or failure modes
Destructive testing intentionally damages or destroys the test specimen to determine properties such as tensile strength, impact resistance, or failure modes that cannot be assessed non-destructively.
Question 2: When establishing a calibration interval for measurement equipment, which factor is most important to consider?
- Equipment purchase price
- Usage frequency, measurement criticality, and historical calibration stability (Correct answer)
- Storage location of the equipment
- Equipment manufacturer's country of origin
Correct answer: Usage frequency, measurement criticality, and historical calibration stability
Calibration intervals should be based on how often and critically the equipment is used, past calibration history, and the consequences of out-of-calibration measurements on product quality.
Question 3: In acceptance sampling, the Lot Tolerance Percent Defective (LTPD) represents:
- The target quality level for a supplier's process
- The quality level at which lots should be rejected with a high probability (consumer's risk protection) (Correct answer)
- The average outgoing quality after rectifying inspection
- The AQL specified in the purchase order
Correct answer: The quality level at which lots should be rejected with a high probability (consumer's risk protection)
LTPD (also called Rejectable Quality Level) is the poorest quality level the consumer is willing to accept with only a small probability (typically 10%), defining the consumer's risk point on the OC curve.
Question 4: What is the key difference between precision and accuracy in measurement?
- Accuracy refers to repeatability; precision refers to closeness to truth
- Precision refers to repeatability of measurements; accuracy refers to closeness to the true value (Correct answer)
- They are synonymous in metrology
- Precision applies to attributes; accuracy applies to variables
Correct answer: Precision refers to repeatability of measurements; accuracy refers to closeness to the true value
Precision describes how closely repeated measurements agree with each other (repeatability), while accuracy describes how close a measurement is to the true or accepted reference value.
Question 5: Which sampling plan standard is most commonly referenced for attribute inspection in US manufacturing?
- ISO 3951
- MIL-STD-1916
- ANSI/ASQ Z1.4 (Correct answer)
- ASTM E2234
Correct answer: ANSI/ASQ Z1.4
ANSI/ASQ Z1.4 (formerly MIL-STD-105) is the most widely used attribute sampling standard in US industry, providing sampling plans indexed by AQL for inspection by attributes.
Question 6: What does Average Outgoing Quality (AOQ) represent in acceptance sampling with rectifying inspection?
- The incoming quality level submitted by the supplier
- The average quality of accepted lots after defectives are replaced during rejected lot screening (Correct answer)
- The total defects found during all inspections
- The AQL achieved over a year of production
Correct answer: The average quality of accepted lots after defectives are replaced during rejected lot screening
AOQ is the average fraction defective in outgoing product after applying rectifying inspection, where rejected lots are 100% inspected and all defectives replaced with conforming items.
CQE Inspection and Testing Methods 2
What is 'destructive testing' and when is it typically used?