Sampling Plan Assistant: GB/T 2828.1 Attribute Sampling
What Is Acceptance Sampling?
100% inspection is expensive and destructive testing cannot inspect everything, so acceptance sampling judges the quality of a whole lot from a sample drawn from it. GB/T 2828.1 (identical to ISO 2859-1) is the most common attribute sampling standard: given the lot size N, inspection level and AQL (acceptable quality level), you look up the sample size n and the acceptance number Ac and rejection number Re to form the sampling plan (n, Ac). Choosing the inspection level and AQL correctly is the key to reliable lot disposition.
How to Look Up the Plan
First find the sample size code letter from the lot size and inspection level (general level II, or special levels S-1 to S-4), then cross the code letter with the AQL in the table to get n, Ac and Re. A smaller AQL means a stricter plan: AQL 0.65 accepts the lot with high probability when the lot nonconforming rate does not exceed 0.65%. The tool contains the complete tables; enter lot size, inspection level, AQL and severity (normal, tightened or reduced) and it generates the plan directly.
How to Decide on Nonconforming Items
If the number of nonconforming items in the sample is Ac or less, accept the lot; if it is Re or more, reject it. Note that GB/T 2828.1 is lot-by-lot sampling: acceptance does not mean the lot is completely conforming but that it meets the protection level of the AQL. After consecutive rejected or accepted lots, switch to tightened or reduced inspection per the standard switching rules, which the tool applies and flags automatically to avoid manual table errors.
Step-by-Step Usage
Determine the lot size N and AQL, choose the inspection level and plan type (single or double sampling), generate n, Ac and Re, run the plan with random sampling, then decide and record. Double sampling reduces the average sample size, and special inspection levels suit destructive or expensive testing. Record and summarize sampling results regularly to support future adjustments of AQL and inspection levels; the tool works online and can add an AI interpretation of the plan meaning.