1. OPERATIONS MANAGEMENT: Creating Value Along the Supply Chain,
Canadian Edition
Robert S. Russell, Bernard W. Taylor III, Ignacio Castillo, Navneet Vidyarthi
CHAPTER 3 SUPPLEMENT
Acceptance Sampling

2. Lecture Outline Single-Sample Attribute Plan
Operating Characteristic Curve
Developing a Sampling Plan with Excel
Average Outgoing Quality
Double - and Multiple-Sampling Plans

3. Acceptance Sampling
Accepting or rejecting a production lot based on the number of defects in a sample
Not consistent with TQM or Zero Defects philosophy
producer and customer agree on the number of acceptable defects
a means of identifying not preventing poor quality
percent of defective parts versus PPM
Sampling plan
provides guidelines for accepting a lot

4. Single–Sample Attribute Plan
Single sampling plan
N = lot size
n = sample size (random)
c = acceptance number
d = number of defective items in sample
If d ≤ c, accept lot; else reject

5. Producer’s and Consumer’s Risk
AQL or acceptable quality level
proportion of defects consumer will accept in given lot
 or producer’s risk
probability of rejecting a good lot
LTPD or lot tolerance percent defective
limit on the number of defectives the customer will accept
β or consumer’s risk
probability of accepting a bad lot

6. Producer’s and Consumer’s Risk
Sampling Errors
Good Lot
Bad Lot
Accept
Reject
No Error
Type I Error
Producer’ Risk
Type II Error
Consumer’s Risk

7. Operating Characteristic (OC) Curve
Shows probability of accepting lots of different quality levels with a specific sampling plan
Assists management to discriminate between good and bad lots
Exact shape and location of the curve is defined by the sample size (n) and acceptance level (c) for the sampling plan

8. OC Curve

9. Developing a Sampling Plan with OM Tools
ABC Company produces mugs in lots of 10,000. Quality contracts require producer’s risk of 0.05 with an AQL of 1% defective and a consumer’s risk of 0.10 with a LTPD of 5% defective. What size sample and what acceptance number should ABC use to achieve performance measures called for in the sampling plan?
N = 10,000 α = 0.05
β = 0.10
AQL = 1%
LTPD = 5%
n = ?
C=?

10. Average Outgoing Quality (AOQ)
Expected number of defective items that will pass on to customer with a sampling plan
Average outgoing quality limit (AOQL)
maximum point on the curve
worst level of outgoing quality

11. AOQ Curve

12. Double-Sampling Plans
Take small initial sample
If # defective ≤ lower limit, accept
If # defective > upper limit, reject
If # defective between limits, take second sample
Accept or reject based on 2 samples
Less costly than single-sampling plans

13. Multiple-Sampling Plans
Uses smaller sample sizes
Take initial sample
If # defective ≤ lower limit, accept
If # defective > upper limit, reject
If # defective between limits, resample
Continue sampling until accept or reject lot based on all sample data

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