Sampling Plans & Acceptance Sampling Flashcards

Skip-lot sampling is most appropriately applied when:

Answer: A supplier has demonstrated consistently high quality over an extended period

Skip-lot sampling reduces inspection frequency by sampling only a fraction of submitted lots, and is appropriate only when a supplier has established a strong history of submitting conforming lots.

In sequential sampling, after inspecting each item the inspector makes a decision to:

Answer: Accept the lot, reject the lot, or continue sampling

Sequential sampling evaluates one item at a time and plots cumulative results against acceptance and rejection lines, making an accept, reject, or continue decision after each unit.

Average Total Inspection (ATI) is a metric that measures:

Answer: The average number of units inspected per lot, including 100% inspection of rejected lots under rectifying inspection

ATI accounts for the sample inspection of accepted lots plus the 100% screen of rejected lots, giving the expected total number of items inspected per lot over the long run.

Under ANSI/ASQ Z1.4, the inspection level primarily determines:

Answer: The relationship between lot or batch size and sample size

The inspection level controls the amount of inspection relative to lot size by mapping lot size ranges to sample size code letters, which then index into sampling plan tables.

A Type A OC curve differs from a Type B OC curve in that Type A applies to:

Answer: Isolated lots, while Type B applies to a continuing series of lots from an ongoing process

Type A OC curves are constructed for isolated individual lots using the hypergeometric distribution, while Type B curves apply to lots from a continuing process using the binomial or Poisson distribution.

In a variables acceptance sampling plan using the k-method, a lot is accepted when:

Answer: The sample mean is at least k standard deviations away from the nearest specification limit

The k-method accepts the lot when (X̄ − LSL)/σ ≥ k and/or (USL − X̄)/σ ≥ k, ensuring the process mean is sufficiently far from specification limits.

Chain sampling (ChSP-1) allows a lot with one defective item to be accepted if:

Answer: The preceding 'i' samples each had zero defectives

In ChSP-1, a lot with exactly one defective can be accepted provided the previous i samples (under the same plan) each contained zero defectives, borrowing quality history to make the decision.