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Chapter 10 Supplement. Acceptance Sampling. Available on Student CD-ROM and Online Learning Centre. Sampling Plans. Acceptance sampling : Form of inspection applied to lots or batches of items before or after a process, to judge conformance with predetermined standards
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Chapter 10 Supplement Acceptance Sampling Available on Student CD-ROM andOnline Learning Centre
Sampling Plans • Acceptance sampling: Form of inspection applied to lots or batches of items before or after a process, to judge conformance with predetermined standards • Sampling plans: Plans that specify lot size, sample size, number of samples, and acceptance/rejection criteria • Single-sampling • Double-sampling • Multiple-sampling
1 0.9 0.8 0.7 0.6 0.5 Probability of accepting lot 0.4 0.3 0.2 3% 0.1 0 0 .05 .10 .15 .20 .25 Lot quality (fraction defective) Operating Characteristic Curve Figure 10S-1
1.00 Ideal Not very discriminating Probability of accepting lot “Good” “Bad” 0 Lot quality (fraction defective) Decision Criteria Figure 10S-2
Sampling Terms • Acceptance quality level (AQL): the percentage of defects at which consumers are willing to accept lots as “good” • Lot tolerance percent defective (LTPD): the upper limit on the percentage of defects that a consumer is willing to accept • Consumer’s risk: the probability that a lot contained defectives exceeding the LTPD will be accepted • Producer’s risk: the probability that a lot containing the acceptable quality level will be rejected
1 = .10 0.9 0.8 0.7 0.6 0.5 Probability of accepting lot LTPD 0.4 0.3 “Good” Indifferent “Bad” 0.2 0.1 = .10 0 0 .05 .10 .15 .20 .25 Lot quality (fraction defective) AQL Consumer’s and Producer’s Risk Figure 10S-3
1 .9139 0.9 0.8 .7361 0.7 0.6 .5443 0.5 Probability of acceptance 0.4 .3758 0.3 .2440 0.2 .1493 .0860 0.1 0 0 .05 .10 .15 .20 .25 Fraction defective in lot QC Curve for n = 10, c = 1 Figure 10S-4
Pac = Probability of accepting lot p = Fraction defective N = Lot size n = Sample size Average Quality • Average outgoing quality (AOQ): Average of inspected lots (100%) and uninspected lots
Approximate AOQL AOQ (Fraction defective out) Incoming fraction defective Example 2: AOQ