10S Click to add Chapter Title McGraw-Hill/Irwin Copyright © 2007 by The McGraw-Hill Companies, Inc All 10S-2 Operations Management William J Stevenson 8th edition 10S-3 CHAPTER 10s Acceptance Sampling McGraw-Hill/Irwin Operations Management, Eighth Edition, by William J Stevenson Copyright © 2005 by The McGraw-Hill Companies, Inc All rights 10S-4 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 10S-5 Operating Characteristic Curve Probability of accepting lot Figure 10S.1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 3% 05 10 15 20 25 Lot quality (fraction defective) 10S-6 Decision Criteria Probability of accepting lot Figure 10S.2 1.00 Ideal Not very discriminating “Good” “Bad” Lot quality (fraction defective) 10S-7 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 10S-8 Consumer’s and Producer’s Risk Probability of accepting lot Figure 10S.3 α = 10 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 “Good” Indifferent 0.1 β = 10 0 05 10 AQL LTPD “Bad” 15 20 25 Lot quality (fraction defective) 10S-9 QC Curve for n = 10, c = Probability of acceptance Figure 10S.4 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 9139 7361 5443 3758 2440 1493 0860 10 20 30 40 50 Fraction defective in lot 10S-10 Average Quality  Average outgoing quality (AOQ): Average of inspected lots (100%) and uninspected lots  N − n AOQ = Pac × p   N  Pac = Probability of accepting lot p = Fraction defective N = Lot size n = Sample size 10S-11 AOQ (Fraction defective out) Example 2: AOQ 0.05 0.09 0.1 0.08 0.070.15 0.06 0.2 0.050.25 0.04 0.3 0.03 0.35 0.02 0.01 0.4 0.046 0.074 0.082 0.075 0.061 0.045 0.03 0.019 Approximate AOQL = 082 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 Incoming fraction defective 10S-12 ...10S-2 Operations Management William J Stevenson 8th edition 10S-3 CHAPTER 10s Acceptance Sampling McGraw-Hill/Irwin Operations Management, Eighth Edition, by William J Stevenson Copyright © 2005 by