Acceptance Sampling Plans

Acceptance Sampling Plans

4.1 Acceptance Sampling Basics

It is the process of inspecting a sample of units taken from a batch that is performed for the purpose of accepting or rejecting the entire batch.

Acceptance Sampling

Defensive strategy in the face of possible deterioration in quality.

QUALITY

This is when a batch is accepted or shipped without any inspection.

Zero inspection

Alternative to prosecute a batch

• 100% inspection

Alternative to prosecute a batch

It consists of checking all the items in the batch to remove those that do not meet the established specifications.

DISADVANTAGEIt can lead to further inspection errors and sometimes the productit is damaged.

• It is used in those cases where the products are high risk and if they pass defective, a great economic loss can be generated.

100% inspection

Alternative to prosecute a batch

When the cost of 100% inspection is too high compared to the cost of passing defective units.

When the inspection is carried out with destructive testing.

When the seller has had excellent levels of quality and a reduction in the inspection quantity is desired.

Acceptance Sampling

• Risk of accepting bad batches and rejecting good ones.It provides less information about the product's quality level. More time and knowledge is required to plan and document sampling.

DISADVANTAGES

TYPES OF SAMPLING PLANS

• It is when each unit of the sample is measured a continuous variable and a statistic is calculated with the data.

PLANS BY VARIABLES

• The value of such a statistic is compared with a value of tables, with which the whole batch will be accepted or rejected.

When each item in the sample is classified as conforming or non-conforming; The number of non-conformers is used to accept or reject the batch.

PLANS BY ATTRIBUTES

POR ATRIBUTOS

If the number of defective items is less than or equal to a certain number c the batch is accepted; otherwise it is rejected.

n articles

• Simple sampling plan

Sampling by attributes: single, double, and multiple

N=6000; n=200; c=2

c= Acceptance number

BY ATTRIBUTES

Plan de muestreo de aceptación por atributos (N,n,c)

BY ATTRIBUTES

Attribute-based plan in which up to two samples can be taken to decide whether a batch is accepted or rejected.

• Plan de muestreo doble

BY ATTRIBUTES

Example:From a batch of 3 000 pieces, a sample n1= 80 is taken:Accept the lot; if the defective units are less than or equal to c1 = 1 Reject the lot; If the defective parts are greater than C2 = 4. Take a second sample of n2 = 80 units when neither of the two previous cases occurs. If the number of defective units in the two samples is less than or equal to c2 = 4, the batch is accepted; but if it is larger, the batch is rejected.

• Double sampling plan

BY ATTRIBUTES

• Multiple Sampling Plan

Attribute-based plan that consists of a generalization of the double sampling plan, where two or more samples can be extracted to accept or reject the batch.

Acceptance sampling is a particular form of inspection, inthat batches are simply accepted and rejected, but it does not improve the quality.