Interactive quality tool / sampling plan

AQL,
explained.

Build a defensible planning estimate, understand the tradeoffs, and know when the table in your customer requirement still wins.

Important boundaryThis is an educational planning aid modeled on common ANSI/ASQ Z1.4-style bands. It is not a substitute for a licensed standard, customer specification, or a risk-based decision for critical characteristics.
01 / define the lot
02 / define the risk
Planning estimate / lot 500 / level II

Inspect 50 units.

Accept the lot at 5 major defects; reject at 6.

AQL 1.0 / major class
How to use the result

Write the rule before the lot arrives.

Put the lot definition, characteristic class, inspection level, AQL, sample, and Ac/Re rule in the purchase order or control plan. Then record the actual sample and disposition.

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What AQL actually means

AQL is an acceptance-sampling parameter. It describes a long-run quality level associated with a sampling plan; it does not mean that every accepted lot may contain that percentage of defects, and it does not make an incapable process acceptable.

Three decisions that matter more than the decimal

  1. Define the lot. A lot should be a meaningful, identifiable quantity made under reasonably consistent conditions.
  2. Classify the characteristic. Critical, major, and minor defects deserve different consequences. Never let a favorable average hide a critical failure.
  3. Define the reaction. If the sample fails, decide in advance whether to reject, screen, contain, request supplier action, or escalate to the customer.

When sampling is the wrong tool

Use 100% inspection or a validated process decision when a defect can create serious harm, when the customer requires it, when the lot is too small to sample sensibly, or when the process is unstable. AQL should sit inside a control plan, not stand in for one.