Specify Two Operating-Characteristic Points Before Choosing a Sampling Plan

The statistical question

An operating-characteristic curve links incoming nonconforming proportion to the probability of accepting a lot. One way to choose a single-sample plan is to specify two desired points on that curve and then find a suitable n,c plan. The two points express different protection requirements. They must be stated as probabilities at identified incoming-quality levels, not as observed sample percentages.

Primary reference: NIST Engineering Statistics Handbook.

An illustrative review example

Consider a hypothetical request that lots at a 1% incoming level should be accepted about 95% of the time, while lots at an 8% level should be accepted only about 10% of the time. The request contains two coordinate pairs: 0.01,0.95 and 0.08,0.10. It does not itself identify an integer sample size or acceptance count. No plan has been solved or approved in this illustration.

Prepare the evidence for discussion

Write the two points in separate rows, name which party owns each protection requirement, and identify the distributional and lot-size basis used by the analyst. Preserve any mismatch when an available integer plan only approximates the target points. For a machinery-component proposal, use the resulting plan reference in the incoming inspection scope and keep machine-performance acceptance criteria in their own trial record.

Two acceptance-protection points

This blank worksheet is for your own project. It contains no H M machine trial result.

Customer Questions

Primary References

These references support the technical principles discussed in this guide. The worked examples and review questions are educational.

• Primary reference: NIST Engineering Statistics Handbook