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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Sampling at the end of a manufacturing process provides a check on the adequacy of the quality control procedures of the manufacturing department. Some applications require special unique sampling plans, so an understanding of how a sampling plan is developed is important. In the construction of a lot by lot single sampling plan, four parameters must be determined prior to determining the sample size and acceptance number.

The sampling will continue until a defect is found. For large lots, the non-replacement of the sampled product does not affect the probabilities. Random spot-checking may sometimes be used when a process is in statistical control.

The nomograph is used for fraction defective sampling plans. 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.

Larson Nomogram – iSixSigma

For this example, the lot size is pieces. Audit sampling is used where the manufacturing quality controls are known to be working correctly. A sample size n is selected randomly from the lot. This licensing tag was added to this file as part of the GFDL licensing update. Nomographs were popular before there were larskn.


File: – Wikimedia Commons

For this example, the differences increase slightly as the curve approaches the tail. As the number of quality characteristics being checked increases, the effectiveness of the inspector decreases.

The intersection will yield the sample size and acceptance number. The L may be modified for any value of b.

The Thorndike chart is used for the following sampling plans:. They may be determined by nomograamm customer, special studies, or past experience. Since computers are not allowed at the CQE exam, the nomographs may come in handy. The AOQ and OC curve, when used together, describe the characteristics of the sampling plan and the risks involved. The following other wikis use this file: A sample is selected and checked for various characteristics. Using the Poisson to calculate probabilities associated with various sampling plans is relatively simple because the Poisson tables can be used.

When n is large and p is small, the Poisson distribution formula may be used to approximate the binomial. Also, the sampling risks involved are not known. 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 homogramm sampling plans.


If c is in terms number of defects, laraon AIQ or abscissa on the OC curve is in terms of defects per unit. Accepting or rejecting a lot is analogous to not rejecting or rejecting the null hypothesis in a hypothesis test.

The L is moved across the chart until one of the acceptance number curves goes through both the a value on the inside vertical scale and the Nomogramk value on the inside horizontal scale. The sample size is determined as follows: The letter n represents the sample size. Views View Edit History. After a certain point, a larger sample will not yield more information. The product may be grouped into lots or may be single pieces from a continuous operation.


A Nomograph is a paper slide rule that helps to simplify certain computations. Like the binomial nomograph, it may also be used nomorgamm determine sample sizes and acceptance numbers for sampling plan applications.

These distributions were covered in the Basic Probability chapter and are reviewed here. The curved lines in the body of the chart represent the cumulative number of occurrences or successes that are of interest. If the process or quality ladson have broken down, the sampling procedures will prevent defective products from going any farther.