The essential elements and procedures of the most commonly used sampling systems are as follows
· Acceptance Sampling.
Sampling inspection in which decisions are made to accept or not accept a product or service. The methodology that deal with procedures by which decisions to accept or reject are based on the results of the inspection of samples.
· Acceptable Quality.
The maximum percentage or proportion of variant units in a lot or batch that can be considered satisfactory as average.
· Limiting Quality.
The percentage or proportion of variant units of a lot or batch that will be restricted to a specified value.
· Average Outgoing Quality.
The average outgoing quality is the maximum outgoing defective rate.
· Acceptance Number.
The acceptance number is the maximum number of variants in the sample that will allow acceptance of the lot or batch.
· Reject Number.
The reject number is the minimum number of variants in the sample that will cause the lot or batch to be rejected.
· Single Sampling Procedure.
A single sampling procedure is a sampling system where acceptance is reached after the inspection of a single sample.
· Double Sampling Procedure.
The acceptance decision will only be reached after two samples have been inspected. The samples do not have to be of the same size. The double sampling system works as follows: select 20 units from the batch at random and inspect them. If there is one or no defective unit accept the lot. If there is three or more defective units reject the lot. If there are exactly two units defective draw another random sample of 25 units. Add the number of defective units in the first sample to the number of defective units in the second sample. If the total number of defective units is two accept the lot.
· Multiple Sampling Procedure.
A multiple sampling procedure is a sampling system where acceptance will be reached after three or more samples have been inspected. The samples are usually the same size. This procedure works the same way as double sampling except that there are more than two stages. Multiple sampling requires less total inspection than either single or double sampling.
· Sequential Sampling Procedure.
A sequential sampling procedure is a sampling system where an acceptance decision is made on the inspection of each unit in the sample.