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8389081 
Journal Article 
TNT ZERO ACCEPTANCE NUMBER SAMPLING 
Calvin, TW 
1977 
35-39 
Tightened/normal/tightened (TNT) sampling inspection is a scheme involving switching between two sampling plans. MIL-STD-105D contains a scheme with a fixed sample size but with two different acceptance criteria. TNT sampling can also be accomplished by maintaining the acceptance criteria and switching between two sample sizes. This approach is particularly appealing with zero acceptance number plans. The usual zero acceptance number operating characteristics (OC) curve decreases exponentially, producing a very severe sampling plan. Switching between two sample sizes with zero acceptance number creates an inflection point in the OC curve similar to that achieved in chain sampling. The result is an improved probability of acceptance at low percent defective where the smaller sample size dominates. These sampling plans are useful in small lot situations and in situations where it is beneficial to accept lots based on samples containing no defects.