Sampling or inspection by attributes is applied to units of a lot or unit production and consists of examining a unit of product or a characteristic and classifying it as "good" or "defective". The action to be taken is decided by counting the number of defects or defective units found.
In order to carry out a sampling and inspection by attributes, the following guidelines and tables should be used The guidelines and tables indicated in the standards and regulations should be used to carry out an attribute sampling and inspection. According to these standards, prior to the sampling plan should be established: single, double or multiple, the level of inspection should be established: normal, reduced or strict, and the inspection level should be classified as follows: normal, reduced or strict.
or strict, the defects must be classified as: major critical or minor, and the acceptable quality level (AQL) for a given defect or group of defects must be indicated defects.