Quality Control Procedures Flashcards

In a double sampling plan, when is a second sample required?

Answer: When the first sample result falls between the acceptance and rejection numbers

A second sample is drawn only when the first sample result is inconclusive — above the accept number but below the reject number.

Which statistical measure best describes process spread in a capability study?

Answer: Standard deviation (sigma)

Standard deviation quantifies the spread of individual measurements and is the basis for capability indices like Cp and Cpk.

What is Average Outgoing Quality Limit (AOQL) in acceptance sampling?

Answer: The maximum average defective rate in accepted lots after inspection and replacement

AOQL is the worst-case average quality of lots that pass inspection, accounting for 100% inspection of rejected lots.

A u-chart is used to monitor:

Answer: The number of defects per unit when sample size varies

The u-chart tracks defects per unit and adjusts control limits for varying sample sizes, unlike the c-chart.

Which approach to quality improvement focuses on reducing variation to achieve near-zero defects at 3.4 DPMO?

Answer: Six Sigma

Six Sigma targets 3.4 defects per million opportunities, equating to 6 standard deviations between the process mean and the nearest specification limit.

In a Shainin DOE approach, what is the 'Red X' concept?

Answer: The dominant root cause variable responsible for most of the variation

Dorian Shainin's Red X identifies the single most dominant variable causing product variation or defects.

What distinguishes a nonconformance from a defect in quality control terminology?

Answer: A nonconformance is any failure to meet a specified requirement; a defect additionally implies fitness-for-use failure or safety concern

Nonconformance refers to any deviation from specifications, while 'defect' carries legal implications regarding fitness for use.