Lecture Operations management: Creating value along the supply chain (Canadian edition) - Chapter 3S

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.. Average Outgoing Quality (AOQ)[r]

Robert S Russell, Bernard W Taylor III, Ignacio Castillo, Navneet Vidyarthi

CHAPTER SUPPLEMENT

Acceptance Sampling

OPERATIONS MANAGEMENT:

Lecture Outline

—Single-Sample Attribute Plan —Operating Characteristic Curve

—Developing a Sampling Plan with Excel —Average Outgoing Quality

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

Single–Sample Attribute Plan

• Single sampling plan

• N = lot size

• n = sample size (random) • c = acceptance number

• d = number of defective items in sample

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

Producer’s and Consumer’s Risk Sampling Errors G oo d Lo t B ad L ot Accept Reject

No Error Type I Error

Producer’ Risk

Type II Error

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

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 = ?

Average Outgoing Quality (AOQ)

—Expected number of defective items that will pass

on to customer with a sampling plan

—Average outgoing quality limit (AOQL)

Double-Sampling Plans

— Take small initial sample

— If # defective ≤ lower limit, accept — If # defective > upper limit, reject

— If # defective between limits, take second sample

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

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