Acceptance Sampling

By: Cori RosoffPenn State UniversityOISM 470W

Short Synopsis

Acceptance sampling DefinedWhen is acceptance sampling useful?The risks associated with acceptance sampling

Short Synopsis

Disadvantages of acceptance samplingApplication of acceptance samplingMoonLight Jeans example

Acceptance Sampling DefinedAcceptance Sampling is a form of inspection that is used to determine whether or not goods are coherent with a set standard of quality

Acceptance SamplingHow can this tool be used in your organization?

When is Acceptance Sampling useful?When product testing is destructiveexpensivetime consuming

When developing new products

When is Acceptance Sampling useful?

When dealing with new suppliers

When a suppliers product has had excellent quality in the past

Risks of Acceptance SamplingProducers RiskThe risk associated with a producer rejecting a lot of materials that actually have good qualityAlso referred to as a Type I Error

Risks of Acceptance SamplingConsumers RiskThe risk associated with a consumer accepting a lot of materials that actually have poor qualityAlso referred to as a Type II Error

Acceptance Sampling

Acceptance sampling is a process that helps to determine whether to accept or reject the sample being observed

Disadvantages of acceptance sampling

The process of the goods being inspected is not improved

When can acceptance sampling be applied?At any point in productionThe output of one stage is the input of the next

When can acceptance sampling be applied?Sampling at the Input stagePrevents goods that dont meet standards from entering into the processThis saves rework time and money

When can acceptance sampling be applied?Sampling at the Output stageCan reduce the risk of bad quality being passed on from the process to a consumer

This can prevent the loss of prestige, customers, and money

When can acceptance sampling be applied?Sampling at the Process stage Can help adjust the process and reduce the amount of poor quality in productionHelps to determine the source of bad production and enables return for reprocessing before any further costs may be incurred

Typical Application of Acceptance SamplingA vendor delivers a product to a manufacturing companyThe product is a raw material used by the company

Typical Application of Acceptance SamplingA sample of the shipment is takenQuality characteristics of the units in the sample are inspected.

Typical Application of Acceptance SamplingBased on the observations made, the decision is made to either accept or reject the entire shipment

Typical Application of Acceptance SamplingThe decision to accept or reject the shipment is based on the following set standards:Lot size = NSample size = nAcceptance number = cDefective items = dIf d c, reject lot

Acceptance Sampling PlanMr. Smith owns and operates a manufacturing plant.

He receives a shipment of 1,000 sheets of glass.

Of the shipment, Mr. Smith chooses to sample 50 sheets.

Acceptance Sampling Plan

If more than 2 are defective, he is sending back the entire shipment to the supplier.

Mr. Smith observes 5 defective sheets of glass.

Acceptance Sampling Plan Therefore, according to the set standards mentioned above:

N = 1,000 n = 50 c = 2 d = 5

Acceptance Sampling Plan What should Mr. Smith do in reference to the number of defective items observed????

Acceptance Sampling Plan Remember, if d > c, reject lotSince c = 2, and d = 5Mr. Smith should reject the lot of 1,000 sheets of glass

MoonLight Jeans

MoonLight Jeans store receives a shipment of 300 pairs of jeans from its warehouse.It is common practice for the store to sample 5% of the total received.The acceptance number under any and all circumstances for MoonLight Jeans is 10.

MoonLight Jeans

Of the 15 pairs of jeans observed, 2 were defective.

What conclusion should the store manager come to based on this information?

MoonLight JeansThe store manager has just found out that the clerk who inspected the samples made a huge mistake

The actual number of defective pairs of jeans sampled was 12.

MoonLight JeansWhat type of risk is involved with the error made at MoonLight Jeans?How might this error affect the store and their customers?

SummaryAcceptance Samplinga form of inspection that is used to determine whether or not goods are coherent with a set standard of qualityIt does not improve the process that the products are derived from

Summary, cont

Uses of Acceptance Sampling

RisksProducers RiskConsumers Risk

Summary, contStages of Inspection Input StageProcess StageOutput StageExample Sampling PlanMoonLight Jeans Example

Works CitedCanavos, George C. and Don M. Miller. Custom Edition of Introduction to Business Statistics 2e. USA: Brooks/Cole Publishing Company, 2001.Foster, S. Thomas. Managing Quality: An Integrative Approach. New Jersey: Prentice-Hall Inc., 2001.Montgomery, Douglas C. Introduction to Statistical Quality Control. USA: John Wiley & Sons, Inc., 1996.

Works Cited, contStarbird, S. Andrew. The Effect of Acceptance Sampling and Risk Aversion on the Quality Delivered by Suppliers. Journal of the Operational Research Society v45 (1994): 309-320.Wetherill, Barrie G. Sampling Inspection and Quality Control. Great Britain: Butler & Tanner Ltd, 1969.

The set standard of quality is determined by a quality control group to ensure that both incoming and outgoing goods are coherent to quality standards.Think of a particular company (manufacturing, for example) that you would like to work forthink of how this theory of acceptance sampling may apply. When would you apply the inspection...at the beginning, in the middle, or at the end of the process? How would you determine the standards of quality? Acceptance sampling is most useful when product testing is destructive, expensive, time consuming, or even when product liability risks are significant (Starbird). It will help reduce costs to the company and ensure a set standard of quality.When dealing with new suppliers, it may be necessary to inspect the incoming goods to ensure that their quality standards are in line with yours. When a suppliers products has had excellent quality in the past, it may not be necessary to perform 100% sampling. Acceptance sampling will just ensure that they are maintaining their quality.Acceptance sampling does not in fact improve the process that the goods being inspected are derived from. It only points out the defects of the products and may in fact aid the inspector to find the source of the problem.In this example, the input is the tree. The output are the wood shingles that are produced from the tree, which later become the input for the house that is being built.By sampling the tree from the previous example, the company can avoid cutting down a dead or hollow tree before it is turned into wood chips. This will help prevent rework time to cut down another tree and money for the labor used.If the company doesnt inspect the trees before they are cut down and they are already cut into wood chips, they can inspect them before they are used to build the house. This can reduce the risk of the house falling apart.If the company inspects the wood after it is cut down but before it is cut into wood chips it will reduce the amount of poor quality chips that it produces. This way, they will know where the bad trees are coming from, and will not incur the cost of passing on bad wood chips.A quality control team should devise a set standard of quality for the goods to adhere to.Based on the set standards and using the data collected, if d < c MoonLight Jeans should accept the lot. In this case, the store manager of MoonLight Jeans observed that there were only 2 defective pairs of jeans out of the 15 observed, and the acceptance number is 10. This means that, where 2