Operations management by stevenson 9th ch10s

McGraw-Hill/Irwin Copyright © 2007 by The McGraw-Hill Companies, Inc.. Stevenson Operations Management 8 th edition... CHAPTER 10s Acceptance Sampling McGraw-Hill/Irwin Copyright © 2005

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10S

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William J Stevenson

Operations Management

8 th edition

CHAPTER

10s

Acceptance Sampling

McGraw-Hill/Irwin Copyright © 2005 by The McGraw-Hill Companies, Inc All rights Operations Management, Eighth Edition, by William J Stevenson

reserved.

Sampling Plans

inspection applied to lots or batches of

items before or after a process, to judge

conformance with predetermined

standards

size, sample size, number of samples,

and acceptance/rejection criteria

 Single-sampling

 Double-sampling

 Multiple-sampling

Operating Characteristic Curve

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Lot quality (fraction defective)

3%

Figure 10S.1

Decision Criteria

0

1.00

Lot quality (fraction defective)

“Good” “Bad”

Ideal

Not very discriminating

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

Consumer’s and Producer’s Risk

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Lot quality (fraction defective)

α = 10

β = 10

“Good”

AQL

“Bad”

Indifferent

LTPD

Figure 10S.3

QC Curve for n = 10, c = 1

Figure 10S.4

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Fraction defective in lot

.9139 7361

.5443 3758

.2440

.1493 0860

Average Quality

Average of inspected lots (100%) and

uninspected lots

AOQ Pac p N n

N

= ×  − 

Pac = Probability of accepting lot

p = Fraction defective

N = Lot size

n = Sample size

Example 2: AOQ

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

Approximate AOQL = 082

Incoming fraction defective