CQI Sampling Plans & Acceptance Sampling 2 — Questions and Answers
Question 1: Consumer's risk (β) in acceptance sampling is the probability of:
- Rejecting a good lot at AQL quality
- Accepting a bad lot at the LTPD quality level (Correct answer)
- Finding the true defect rate in the population
- Exceeding the prescribed sample size
Correct answer: Accepting a bad lot at the LTPD quality level
Consumer's risk (β) is the probability that a bad lot at the Lot Tolerance Percent Defective (LTPD) quality level is incorrectly accepted, representing the risk borne by the customer.
Question 2: LTPD stands for:
- Lot Tolerance Percent Defective (Correct answer)
- Lower Threshold Production Defect
- Lot Total Process Deficiency
- Limiting Tolerance Product Defect
Correct answer: Lot Tolerance Percent Defective
LTPD (Lot Tolerance Percent Defective) is the poorest quality level that a consumer is willing to accept in an individual lot, typically associated with a consumer's risk of 10%.
Question 3: ANSI/ASQ Z1.9 provides acceptance sampling plans based on:
- Attribute data (pass/fail inspection)
- Variables data (actual measurements) (Correct answer)
- Sequential item-by-item inspection
- Continuous production sampling
Correct answer: Variables data (actual measurements)
ANSI/ASQ Z1.9 uses variables (measurement) data to make accept/reject decisions, offering smaller sample sizes than its attributes counterpart Z1.4 for the same protection.
Question 4: Rectifying inspection is a procedure in which:
- All defective items in rejected lots are screened and replaced with conforming items (Correct answer)
- Inspectors are recertified after every rejection
- Only critical defects trigger a full lot inspection
- Inspection responsibility is transferred to the supplier
Correct answer: All defective items in rejected lots are screened and replaced with conforming items
Rectifying inspection requires that rejected lots be 100% inspected and all defectives replaced with good items, which enables calculation of metrics like AOQL.
Question 5: The Average Outgoing Quality Limit (AOQL) represents:
- The minimum outgoing quality a process can achieve
- The maximum average outgoing quality over many lots with rectifying inspection (Correct answer)
- The customer's maximum acceptable AQL value
- The average defect rate measured across all suppliers
Correct answer: The maximum average outgoing quality over many lots with rectifying inspection
The AOQL is the worst average outgoing quality that will be passed to the consumer over the long run when rejected lots are rectified; it sets an upper bound on average outgoing defect levels.
Question 6: Under ANSI/ASQ Z1.4, tightened inspection is initiated when:
- Any single lot is rejected during normal inspection
- Two out of five consecutive lots are rejected on original inspection under normal inspection (Correct answer)
- The supplier's AQL exceeds the contractual limit once
- The consumer requests a supplier quality audit
Correct answer: Two out of five consecutive lots are rejected on original inspection under normal inspection
The switching rule to tightened inspection is triggered when 2 out of 5 consecutive lots are rejected on original inspection while on normal inspection, indicating a deteriorating process.
Question 7: Under ANSI/ASQ Z1.4, reduced inspection may be considered when:
- The last 5 lots have all been accepted under normal inspection
- Ten consecutive lots have been accepted under normal inspection with a satisfactory production record (Correct answer)
- The supplier requests reduced sampling to cut costs
- No defectives are found in three consecutive lots under tightened inspection
Correct answer: Ten consecutive lots have been accepted under normal inspection with a satisfactory production record
Reduced inspection requires 10 consecutive lots accepted under normal inspection, a satisfactory production record, and approval from the responsible authority before switching.
CQI Sampling Plans & Acceptance Sampling 2
Consumer's risk (β) in acceptance sampling is the probability of: