CQI Sampling Plans & Acceptance Sampling 1 — Questions and Answers
Question 1: What does AQL stand for in acceptance sampling per ANSI/ASQ Z1.4?
- Allowable Quality Level
- Acceptance Quality Limit (Correct answer)
- Average Quality Loss
- Adjusted Quality Level
Correct answer: Acceptance Quality Limit
AQL stands for Acceptance Quality Limit, defined as the quality level that is the worst tolerable process average when a continuing series of lots is submitted for acceptance sampling.
Question 2: In a single sampling plan, a lot is rejected when the number of defectives found in the sample is:
- Equal to the acceptance number (Ac)
- Less than or equal to the acceptance number (Ac)
- Greater than the acceptance number (Ac) (Correct answer)
- Equal to half the rejection number (Re)
Correct answer: Greater than the acceptance number (Ac)
A lot is rejected when the number of defectives exceeds the acceptance number (Ac), meaning the rejection number (Re) is typically Ac + 1.
Question 3: The Operating Characteristic (OC) curve of a sampling plan illustrates the relationship between:
- Sample size and lot size
- Probability of lot acceptance and incoming lot quality (Correct answer)
- AQL and LTPD values
- Producer's risk and consumer's risk
Correct answer: Probability of lot acceptance and incoming lot quality
The OC curve plots the probability of accepting a lot (Pa) against the actual lot fraction defective, showing how well the sampling plan discriminates between good and bad lots.
Question 4: The producer's risk (α) in acceptance sampling is the probability of:
- Accepting a lot at the LTPD quality level
- Rejecting a lot that meets the AQL (Correct answer)
- Finding zero defects in the sample
- Accepting a lot with defects above the AOQL
Correct answer: Rejecting a lot that meets the AQL
Producer's risk (α) is the probability that a good lot meeting the AQL is incorrectly rejected, representing the risk borne by the supplier.
Question 5: In acceptance sampling, the AQL represents:
- The worst average process quality level still considered acceptable (Correct answer)
- The maximum defect level permitted in any single lot
- The quality level at which 50% of submitted lots are accepted
- The minimum sample size required for inspection
Correct answer: The worst average process quality level still considered acceptable
The AQL is the worst tolerable process average quality level for a continuing series of lots; lots at AQL quality have a high probability of acceptance.
Question 6: In a double sampling plan, if the number of defectives in the first sample falls between Ac1 and Re1, the inspector should:
- Accept the lot immediately
- Reject the lot immediately
- Draw a second sample and combine results (Correct answer)
- Place the lot on hold pending supplier response
Correct answer: Draw a second sample and combine results
When first-sample results are inconclusive (between Ac1 and Re1), a second sample is drawn and the combined defectives from both samples are compared to Ac2 and Re2.
Question 7: Under ANSI/ASQ Z1.4, which inspection level is used as the default unless otherwise specified?
- Level I
- Level II (Correct answer)
- Level III
- Level S-1
Correct answer: Level II
Inspection Level II is the default general inspection level in ANSI/ASQ Z1.4 and provides a balanced trade-off between sample size and discrimination.
CQI Sampling Plans & Acceptance Sampling 1
What does AQL stand for in acceptance sampling per ANSI/ASQ Z1.4?