What does Acceptance Sampling mean?

Acceptance Sampling:

Acceptance Sampling is a technique of Product control. Product control is a method of statistical quality control in which the quality of the product is controlled while the product is ready to dispatch or sell to the final customers. In acceptance sampling, the decision regarding the acceptance or rejection of a whole lot depends upon the quality of the sample drawn from that lot. If the sample is as per the standard (i.e. number of defects on the sample are below acceptance number or acceptance quality limit), then the lot will be accepted otherwise will be rejected. Sampling inspection plans are used in acceptance sampling to reach in the decision regarding acceptance or rejection of a lot. There are two types of risk that may occur in acceptance sampling.

1.      Producer risk

2.    Consumer risk

Read also: What is Statistical Quality Control (SQC)?

Producer risk:

Producer risk is the risk of rejecting good quality product due to the samples of having bad quality. For example, suppose there are 50 apples in a box among which 5 apples are of bad quality. To check the quality of the apple, 5 apples are taken as a sample from that box. Unfortunately, all bad quality apples are selected as a sample and the box is rejected even if remaining 45 apples are of good quality.

Consumer risk:

Consumer risk the risks of accepting bad quality products due to the sample of having good quality. For example, suppose there are 50 apples in a box among which 5 apples are of good quality. To check the quality of the apple, 5 apples are taken as a sample from that box. Unfortunately, all good quality apples are selected as a sample and the box is accepted even if remaining 45 apples are of bad quality.

Read also: Explain Product Control and Process Control.

Types of sampling inspection plans:

1. Single sampling inspection plan:

In single sampling plan, samples (n) are taken from the lot and defected items (d) are counted from that sample. And then the comparison is made between the number of defectives and the acceptance number (c). If the number of defective items is less than or equal to that of acceptance number, then the lot will be accepted otherwise rejected. It has been shown in the following diagram.

Read also: What is control chart?

2. Double sampling inspection plan

In double sampling inspection plan, samples of size n₁ and n₂ are taken from a lot one after another and final decision are made after comparing the number of defectives from the sample n₁ and n₂ either with the same acceptance quality limit or different acceptance quality limit one after another. The steps involved in double sampling inspection plan are presented in the diagram below.

3. Multiple sampling inspection plans

In multiple sampling inspection plans, the samples are taken more than two time and same steps are followed. It is not in practical used.