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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Two parameters are specified in a continuous sampling plan.


To assist in the task, a tool called an L will be used. Views View Edit History. They are also included in various textbooks. Sampling plans may be developed to meet certain criteria and to insure that the specified outgoing quality levels are met. Draw a line from the AQL. The values for the operating characteristic OC curve are obtained directly from the nomograph. The chart shows the inspector what decision to make after each sample is inspected.

This page was last edited on 13 Octoberat They will be provided separately if you have the computer based version of QReview.

NPTEL :: Management – Six Sigma

Find the closest sample size and acceptance number to the intersection point. The manufacturing department, as part of the process or quality control program, may also use lwrson techniques.


As processes become more refined and the process capabilities are known, the need for inspection becomes less important. In no,ogramm sampling, the risks of making a wrong decision are known.

The six methods listed below are widely used. No checking may be warranted when the process capability is known and the probability of defective product is very small. Audit sampling is sampling that is done on a routine basis, but acceptance criterion is not specified. Random spot-checking may sometimes be used when a process is in statistical control.

The most common values to use for a and b are.

The process capability must be known and the chance of defective products arriving at the inspection point must be very small. If a second sample is inspected: If the number of defects or defectives in the first sample exceed c 2the lot is rejected and a second sample is not taken. As the number of quality characteristics being checked increases, the effectiveness of the inspector decreases. They may be determined by your customer, special studies, or past experience.

The letter p is the incoming quality level AIQ and P a is the probability of acceptance. If the process has been controlled satisfactorily, the product would be accepted and passed on to the next organization or customer. The ordinate is the probability of c or fewer occurrences.

The nomograph greatly simplifies and reduces the computational burden involved with solving binomial problems. The probability of larsom is the probability that the number of defects or defective units in the sample is equal to or less than the acceptance number of the sampling plan.


The objective is to find a sample size and acceptance number whose OC curve meets the above parameters.

Sampling plans are hypothesis tests regarding product that has been submitted for an appraisal and subsequent acceptance or rejection. The lot will either be accepted rejected or another sample will be taken.

Larson Nomogram

The first is the frequency of checking f and the second is the clearing number i. 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 Thorndike chart may be used as an alternative to the Poisson tables when determining cumulative probabilities.

Copies of the binomial nomograph and Thorndike chart are included in the appendix. This is sometimes referred to as sampling with replacement although the parts are not physically replaced. The sample size is determined as follows: A periodic audit to verify that conditions have not changed is a recommended practice when products are not checked nomogra,m a routine basis.

There are some minor differences.