QUALITY CONTROL TOOLS FOR PROCESS IMPROVEMENT Chapter 12-Supplement QUALITY CONTROL TOOLS FOR PROCESS IMPROVEMENT McGraw-Hill/Irwin © 2003 The McGraw-Hill Companies, Inc., All Rights Reserved.

LEARNING OBJECTIVES Introduce the basic tools for analyzing processes and quality. Describe acceptance sampling and when it can be used to control quality in services. Introduce statistical process control and describes how and when it can be used to analyze service processes. Define the types of sampling errors that can occur when statistical sampling is used. Distinguish between the statistical analysis of attributes and variables.

THE SEVEN BASIC QUALITY TOOLS Process Flow Diagrams Checksheets Histograms/Bar Charts Pareto Charts Scatterplots Run Charts Cause-and-Effect Diagrams

Exhibit 12S.1 PROCESS FLOW DIAGRAM: DRYCLEANING SERVICE

Exhibit 12S.3 CHECKSHEET

Exhibit 12S.4 EXAMPLE OF A BAR CHART

Exhibit 12S.5 EXAMPLE OF A HISTOGRAM

Exhibit 12S.6 EXAMPLE OF A PARETO CHART

Exhibit 12S.8 EXAMPLE OF A SCATTERPLOT

Exhibit 12S.9 EXAMPLE OF A RUN CHART

Exhibit 12S.10 EXAMPLE OF A CAUSE-AND-EFFECT DIAGRAM

Exhibit 12S.11 THE EIGHT STEP QUALITY IMPROVEMENT PROCESS

TWO BASIC MODELS FOR STATISTICAL QUALITY CONTROL Acceptance Sampling: This involves testing samples after the goods or services have been produced. Statistical Process Control: This involves testing samples of goods or services as they are being produced.

Exhibit 12S.12 THE RELATIONSHIP BETWEEN POPULATION QUALITY AND SAMPLE FINDINGS What the Population Quality Actually Is Good Bad Good Lot Accepted: No Error Bad Lot Accepted: Type II Error or  Good What the Sample Finding Is Good Lot Rejected: Type II Error or  Bad Lot Rejected: No Error Bad

Exhibit 12S.13 OPERATING CHARACTERISTIC CURVE

Exhibit 12S.14 THE NORMAL DISTRIBUTION

PROCESS CAPABILITY Collect data on the process while the process is operating without known causes of variation. Compare the customer’s requirements to the inherent variation of the process.

Exhibit 12S.16 CAPABILITY STUDY

Exhibit 12S.17 SIX-SIGMA QUALITY

Exhibit 12S.20 CHANGES IN MEAN AND DISPERSION OF SAMPLE MEAN DISTRIBUTIONS

KEY TERMS Acceptance Sampling Capability Central Limit Theorem Operating Characteristic Curve Statistical Process Control Type I Error Type II Error Variables