HRN ISO , Larson nomogram, operating characteristic curve of the acceptance plan, statistical quality control attribute acceptance plans, sampling. Fortunately, Larson has determined a nomograph (a graphical calculating Larson’s nomograph can be used as follows: the vertical line on the left-hand side is. From the Larson nomogram, the binomial plan satisfying these specifications is n1⁄, c1⁄ Using the Lieberman and Owen () tables for D1 1⁄(20).

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If c is in terms number of defects, the AIQ or abscissa on the OC curve is in terms of defects per unit. The abscissa on the Thorndike chart is np.

Both the binomial nomograph and the Thorndike chart give the same sample size and acceptance number. Nomogramj or rejecting a lot is analogous to not rejecting or rejecting the null hypothesis in a hypothesis test.

When n is large and p is small, the Poisson distribution formula may be used to approximate the binomial. Retrieved from ” https: This is because they are easier to administer and implement than the other plans and they are very effective.

Both the sample size and acceptance numbers nomotramm be integers. The AOQL is approximately. Although the hypergeometric may be used when the lot sizes are small, the binomial and Poisson are by far the most popular distributions to use when constructing sampling plans.


The rejected lots may be submitted for re-inspection. The most common values to use for a and b are. There are three probability distributions that may be used to find the probability of acceptance. In addition, one hundred percent checking cannot be used when a destructive test is made. Audit sampling is sampling that is done on a routine basis, but acceptance criterion is not specified.


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A quality report is issued and the manufacturing organization will determine what action is to be taken if the material is not acceptable. A chart like the one shown below is specified for various sequential sampling plans. When inspection is performed by attributes, product is classified as good or defective four types of acceptance sampling plans may be used, with lot by lot single sampling plans being the most popular.

Two sample sizes n 1n 2 and two acceptance numbers c 1c 2 or AN 1AN 2 are specified. The lot will either be accepted rejected bomogramm another sample will be taken. The Nomogrmm curve shows the probability of acceptance for various values of incoming quality.

If a onmogramm sample is inspected: For every acceptance sampling plan, the outgoing quality will be somewhat better than the incoming quality because a certain percent of the lots will be rejected and detailed. Draw a line from the AQL. In some cases the lot may be scrapped. Some applications require special unique sampling plans, so an understanding of how a sampling plan is developed is important. The Operating characteristic curve is a picture of a sampling plan.

The process capability must be known and the chance of defective products arriving at the inspection point must be very small. The advantage of this type of sampling plan is that a decision could be made based on a relatively small sample.


This screenshot either does not contain copyright-eligible parts or visuals of copyrighted software, or the author has released it under a free license which should be indicated beneath this noticeand as such follows the licensing guidelines for screenshots of Wikimedia Commons. The random check is used to verify that the process is in control and to report the product quality level.

No checking may be warranted when the process capability is known and the probability of defective product is very small.

Larson Nomogram – iSixSigma

Nomographs were popular before there were computers. This sounds like a logical procedure to many people. They are also included in various textbooks.

A sample size n is selected randomly from the lot. It is also used to approximate the binomial probabilities involving the number of defective parts when the sample n is large and p is very small. The decision is based on the specified criteria and the amount of defects or defective units found in the sample.

The product may be grouped into lots or may be single pieces from a continuous operation. A periodic audit to verify that conditions have not changed is a recommended practice when products are not checked on a routine basis.