Quality Control Procedures Flashcards

What is the Consumer's Risk (Beta risk) in acceptance sampling?

Answer: The probability of accepting a lot at the Lot Tolerance Percent Defective (LTPD) quality level

Consumer's risk (β) is the probability that a bad lot at LTPD quality level will be accepted by the sampling plan.

Which technique is used to quantitatively assess how much each factor and interaction contributes to variation in a DOE?

Answer: Analysis of Variance (ANOVA)

ANOVA partitions total variation into contributions from each factor and interaction, enabling statistical significance testing.

A process produces 50 defects in 1,000 units inspected. What is the Defects Per Unit (DPU)?

Answer: 0.05

DPU = total defects / total units = 50 / 1,000 = 0.05 defects per unit.

What distinguishes 'tightened inspection' from 'normal inspection' in ANSI/ASQ Z1.4?

Answer: Tightened inspection uses a smaller acceptance number for the same sample size, applied after poor lot quality history

Under tightened inspection, the acceptance number is reduced (stricter), triggered when two of five consecutive lots are rejected under normal inspection.

In measurement system analysis, what does 'bias' refer to?

Answer: The systematic difference between the observed average measurement and the reference (true) value

Bias (accuracy) is the offset of the measurement system's average from the true reference value, indicating systematic error.

A Dodge-Romig sampling plan is designed to minimize:

Answer: Total inspection cost (sample + rectifying inspection) for a given AOQL or LTPD

Dodge-Romig plans minimize total inspection (sample plus 100% inspection of rejected lots) while meeting either AOQL or LTPD requirements.

Which quality control concept states that 80% of defects typically come from 20% of causes?

Answer: Pareto Principle

The Pareto Principle (80/20 rule) guides quality teams to focus corrective efforts on the vital few causes that produce most defects.