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Pc - Consumer's risk

In reference to sampling plans, consumer's risk, (Pc), is the probability that a "bad" lot will be accepted. Lots are considered to be bad if they fail a LASP, (Lot acceptance sampling plan). This can be a crucial measurement when implementing six sigma.

This means the chance of a product deemed unsatisfactory to a customer could be accepted by Inspection. Engineers try to keep the ‘Consumer's Risk’ as small as possible, keeping in mind the requirements of users in each specific instance.

The Consumer's Risk of a sampling plan can be estimated as follows… (the Dodge and Romig ‘Sampling Inspection Tables’ defines ‘Consumer's Risk’ tighter than it is defined here)

  • Second, determine the percent defective that the consumer wants to reject. This should be interpreted as the point where the quality is so poor that the consumer would turn it down a large percentage of the time.
  • Third, find this value on an OC curve scale, and use the curve to ascertain the probability of acceptance. This indicates the risk of receiving rejects under conditions assumed in the second step providing the product is of such poor quality it could be actually submitted.

It is possible to calculate the ‘Consumer's Risk’ without plotting the OC curve, however, most are generally interested in the entire area around the percent defective. Due to this, it is a real plus to have a completed OC curve first.

A Consumer's Risk of 10% does not mean that the consumer would have a 10% probability of getting a reject product. It would indicate products such as that would have a 10% probability of being accepted providing they were actually submitted to Inspection. Keep in mind that if the process is running close it’s capability and is close to the shoulder of the curve, then product could be as bad as 9% defective would probably not be produced.


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Last Updated: Saturday, 01-Apr-06 01:21:43 PST