Fundamentals of Quality Control and Improvement, 4th Edition

6Statistical Process Control Using Control Charts

1. 6-1 Introduction and chapter objectives
2. 6-2 Causes of variation
3. 6-3 Statistical basis for control charts
4. 6-4 Selection of rational samples
5. 6-5 Analysis of patterns in control charts
6. 6-6 Maintenance of control charts
7. Summary

Symbols
θ	Parameter
	Estimator
α	Probability of a type I error
β	Probability of a type II error
	Standard deviation of sample mean
σ	Process standard deviation
n	Subgroup or sample size

6-1 Introduction and Chapter Objectives

We have discussed at length the importance of satisfying the customer by improving the product or service. A process capable of meeting or exceeding customer requirements is a key part of this endeavor. Part III of the book deals with the topic of process control and improvement. It provides the necessary background for understanding statistical process control through control charts. In this chapter we build the foundation for using control charts. The objectives of this chapter are to introduce the principles on which control charts are based. The basic features of the control charts, along with the possible inferential errors and how they may be reduced, are presented. Various types of out-of-control patterns are also discussed. In Chapter 7 we examine control ...