You have to design a sampling plan (n, c) that has an OCC that meets certain pre-specified requirements. Generally, the design is based on the following criteria that are related the probability of making of the following errors : accepting a bad lot (P) aid rejecting a good lot (a). The criteria are established subjectively and ultimately should reflect the cost of accepting a bad lot or rejecting a good lot. Needless to say, before a and P values can be specified. one has to decide what is a gold lot and what is a bad lot. Invariably, this is done by specifying the lower/upper limits of fraction defective 0, as illustrated below :
- AQL (Acceptable Quality Level) the fraction defective (n that the user considers acceptable. Thus if a batch were known to have a fraction defective equal to AUL, it should not be rejected.
- LTPD (Lot Tolerance Percent Defective) the fraction defective that defines a bad lot or (me that should be rejected. Of course AOL must be less than LTPD
- Producers Risk (a) the largest allowable probability of rejecting a good lot (due to statistical error). Note that a good lot has fraction defective less than or effectual to AQL (generally, 5 percent).
- Consumers Risk (P) the largest allowable probability of accepting a had (due to statistical error). Note that a bad lot as fraction defective greater than or equal to LTPD (general] y 10 percent).
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