Single and double sampling
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Sampling is selecting a representative subset of a population to make inferences about the whole population. It involves randomly selecting a sample and inspecting it. If the number of defects found exceeds a threshold, the entire lot is rejected. If it is below the threshold, the lot is accepted. Multiple samples may be taken to improve accuracy, with the lot rejected only if the total defects across samples exceeds the threshold. Sampling allows determining characteristics of the whole population while inspecting only a fraction.
Single and double sampling
- 2. WHAT IS SAMPLING? Sampling is the act, process, or technique of selecting a suitable sample, or a representative part of a population for the purpose of determining parameters or characteristics of the whole population.
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- 10. Lot of N Items Random Sample of N - n Items n Items d Defectives Inspect n Items Found in Sample Replace d>c d< c Defectives n Nondefectives Reject Lot Accept Lot 10
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- 15. Lot of N Items Random Sample of N – n1 Items n1 Items Replace d1 Defectives Defectives Inspect n1 Items Found in Sample n1 Nondefectives d1 > c2 d1 < c1 Accept Lot c1 < d1 < c2 Reject Lot Continue (to next slide) 15
- 16. Continue (from previous slide) N – n1 Items Random N – (n1 + n2) Sample of Items n2 Items Replace d2 Defectives Defectives Reject Lot Inspect n2 Items Found in Sample n2 Nondefectives (d1+ d2) > c2 (d1+ d2) < c2 Accept Lot 16
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