ABSTRACT
The control charts discussed in Chapters 3-6 are for handling cases when the qual-
ity characteristic in question is univariate. In most applications, however, the quality
of a product is affected by multiple characteristics of the product. For instance, the
quality of a bottle of soft drink may be affected by the weight, amounts of different
ingredients, quality of the paper or plastic label on the bottle, and so forth. Regard-
ing the quality of a product with a complicated structure (e.g., cars, airplanes, space
shuttles), we can easily list hundreds of quality characteristics that are important to
monitor during its production. As described in Chapter 1, quality is a multifaceted
concept. Garvin (1987) gave eight dimensions to the definition of quality, including
performance, features, reliability, conformance, durability, serviceability, aesthetics,
and perceived quality (cf., Section 1.1). Therefore, most statistical process control
(SPC) applications have multiple quality characteristics involved. Such SPC prob-
lems are often referred to as multivariate SPC (MSPC) problems, which are the main
focus of this chapter.
