Empirical approach for single attributes sampling plans design under normal inspection based on standards COVENIN 3133-1:2001 and MIL-STD-105E

(Received: 2015/05/02 - Accepted: 2015/06/11)An empirical rule is proposed for determining the sample size n to be taken depending on the lot produced size N for a single attributes sampling under normal inspection based on the standards COVENIN 3133-1: 2001 and MIL-STD-105E; also, the acceptance number c for a given level of acceptable quality was calculated, and the corresponding operating characteristic curves were constructed. Two potential regression equations were obtained for calculation of sample size to fit R2 of 99.91% and 99.38% for lot sizes N≤666 and N>666, respectively, in addition, a sampling plan was designed for a lot size of 176,000 units with an acceptable level of quality of 0.65% defectives units. The proposed sampling plan presented a smaller sample size (n=560) than the standard (n=800), with operating characteristic curve very similar to the closest sampling plan recommended by the standard (n=500). The application of the empirical approach is recommended for the design of cheaper sampling plans which in turn are consonant with the rules COVENIN 3133-1: 2001 and MIL-STD-105