AQL Sampling plan and sampling table Level I, Level II, Level III

Sampling plans

Inspection level
The inspection level determines the relationship between the lot or batch size and the sample size. The inspection level to be used for any particular requirement will be as prescribed by the contractor's written procedure.
Three inspection level: I , II , III are given in table 1 for general use. Normally, inspector level II is used. However, inspection level I may be used when less discrimination is needed, or level III may be used for greater discrimination. Four additional special levels: S-1. S-2, S-3, S-4 are given in the same table and may be used where relatively small sample sizes are necessary and large sampling risks can or must be tolerated.

Code letters
Sample sizes are designated by code letters, Table 1 - sampling table shall be use to find the applicable code letter for the particular lot or batch size and the prescribed inspection level.

Obtaining sampling plan.
The AQL and the code letter shall be used to obtain the sampling plan from master table, When no sampling plan is available for a given combination of AQL and code letter, the tables direct the user to difference letter. The sampling size to be used is given by the new code letter, not by the original letter. If the procedure leads to different sample sizes for difference classes of defects, the code letter corresponding to the largest sample size derived may be used for all classes of defects, As an alternative to a single sampling plan with an acceptance number of 0, the plan with an acceptance number of 1 with its correspondingly larger sample size for a designated AQL, may be used.

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Sampling table for sample size and its code letter