Sequential sampling chooses when to stop from the accumulating results. Repeatedly checking an ordinary fixed-sample rule is a different procedure.
The statistical question
In item-by-item sequential acceptance sampling, the accumulating inspected quantity and nonconforming count are compared with defined accept, reject and continue boundaries. Total inspection quantity is an outcome of that scheme. Its average sample number depends on incoming quality. A plan also needs its stated termination or truncation rule; an analyst must evaluate the whole stopping procedure.
An illustrative review example
Imagine two fictional lots assessed using the same sequential scheme. The first reaches a valid stopping boundary after 28 inspected items, while the other continues until 61. These different totals do not prove that the inspector skipped required work. Conversely, repeatedly applying a fixed 50-item pass rule after every new item does not recreate a properly designed sequential plan. The rule and its approved stopping history distinguish the cases.
Prepare the evidence for discussion
Keep the ordered inspection record, cumulative totals, boundary reference, stopping stage and any terminal decision. Ask the quality team how continuing inspection is handled when an operating window ends. Do not copy a generic graph and infer a production release rule. For a component-inspection cost estimate, discuss both the achieved protection and workload distribution before replacing a fixed-sample inspection arrangement.
A sequential quantity is an outcome
This blank worksheet is for your own project. It contains no H M machine trial result.
| Question to resolve | Evidence to retain |
|---|---|
| Ordered observation | Item-level finding sequence |
| Cumulative point | Inspected quantity and findings |
| Stopping boundary | Accept, reject or continue |
| Termination | Approved final or truncation rule |
Customer Questions
Why can inspection quantity differ between lots?
A sequential scheme stops according to accumulated observations and its specified boundaries.
Is average sample number a guaranteed quantity?
It describes expected workload under an incoming-quality basis, not every lot outcome.
Can a fixed-sample test simply be checked repeatedly?
Repeated looks change the stopping procedure and require their own statistical design.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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