Question

A product shipped in lots of size 400 is subject to inspection via ISO Norm 2859. Assuming a single sampling plan operating at General Level III, what would be the sample size and the decision rule under normal inspection if an AQL of 2.5% is being used?

Answer 1

From the table of the single sampling plan, The sample size code selected is:

SINGLE SAMPLING PLAN FOR NORMAL INSPECTION, ANSI/ASQ STANDARD Z1.4-2003 SAMPLE SIZE CODE LETTERS General Inspection Levels Lot Size Special Inspection Levels s2 S3 S4 А A 2 to 8 9 to 15 16 to 25 26 to 50 51 to 90 с D A B C F 91 to 150 D 151 to 280 281 to 500 E E F G 501 to 1200 1201 to 3200

Sample code = "J"

Now, from the AQL table:

Sample Size Co Letter Sample Size 0.065 Re 0.1 AC Re Acceptable Quality Levels (Normal Inspection) 0.15 0.25 0.4 0.65 1 1 .5 2.5 AC Re Acre AC Re AC Re AC Re Ac Re Ac Re 4 6 .5 10 15 AC Re AC Re Acre Ac Ac Re 0 1 0 1 15 8 13 0 1 1 2 D E 2 0 1 F 20 32 0 1 2 2 H 0 1 12 2 3 3 50 80 125 1 2 2 3 K 0 1 1 2 2 3 10 11 14 15 21

The sample size selected should be 80.

For an AQL level of 2.5, the accept point is 5 defects and the reject point is 6 defects. Hence, we will reject the order when there are a minimum of 6 defects in a sample size of 80.