Lec 15 - Acceptance Sampling

Lec 15 - Acceptance Sampling - Accept or reject a lot?...

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Accept or reject a lot? Three approaches to lot sentencing –: 1. Accept with no inspection – C p is 3 or 4; vendor is excellent; has excellent process control 2. 100% inspection – critical component, technology available 3. Acceptance sampling - Goal is decision making, not estimation of fraction defective
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When to Use Acceptance Sampling instead of 100% Inspection Cost/Time of 100% inspection is too high Testing is destructive 100% inspection infeasible – inspection error is great, lack of technology Vendor has good quality history
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Types of Sampling Attributes Variables Single Double Multiple Sequential
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Single, Double, Multiple and Sequential Sampling Plan Single Plan Sample n, accept or reject lot Double Plan – Sample n 1 ; accept, reject or sample n 2 Multiple Plan – Sample n 1 , accept, reject or sample n 2 ; – Sample n 2 , accept, reject or sample n 3 ; etc. Sequential Plan
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Lot Formation Homogeneous Larger better than smaller Conforms with materials-handling systems used in both the vendor and consumer facilities.
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Sample from Lot Must be Randomly Sampled!!! Bias is easy to introduce Use random numbers
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Single-Sampling Plans For Attributes: (specify n and c) N = lot size (assume N very large – special case, if not) n = sample size c = acceptance number r.v. d = observed number of defectives Accept lot if d c number of defectives in sample d is less than or equal to acceptance number c
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Ex: Plan is n=50, c=1. Find prob of accepting
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Lec 15 - Acceptance Sampling - Accept or reject a lot?...

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