Applying the Seven Basic Quality Tools in Software Development

The basic statistical tools for quality control promoted by Ishikawa (1989) are widely used in manufacturing productions . They have indeed become an integral part of the quality control literature, and have been known as Ishikawa's seven basic tools. This chapter describes the application of these tools for process and quality control in software development. There are many ways to analyze software metrics; the applications of Ishikawa's seven tools represent a set of basic operations. Keep in mind that these statistical tools are for process and quality control at the project and organization level and, hence, are useful for project leaders and process experts. In contrast, they do not provide specific information to software developers on how to improve the quality of their designs or implementation. Also, because not all these tools are equally useful for small projects where statistical patterns of parameters of the development process are less obvious, the benefits of statistics may not be realized. The box at the end of the chapter offers specific recommendations for small teams . In addition, although the benefits of these tools have long been proved in manufacturing operations, their use and roles in software development has not been widely recognized. For instance, the use of control charts in manufacturing production can ensure a certain end-product quality once the process is defined and the control limits are set. In software development, however, the process is complex and involves a high degree of creativity and mental activity. It is extremely difficult, if not impossible , to define the process capability of software development in statistical terms. Therefore, achieving statistical process control in software development may mean a lot more than control charting. It may require, for example, new development technology, CASE tools, and the use of defect models and reliability estimating techniques. However, good use of the seven basic tools can lead to positive long- term results for process improvement and quality management in software development.

The following sections begin with a brief description of the tools, followed by a discussion of each tool with examples of its applications. Where appropriate, the influences of these tools on process improvement and on decision making are also described. The examples are either from software engineering literature or from software projects developed at IBM in Rochester, Minnesota. In addition to the seven basic tools, we discuss the relations diagram, which is effective for small team brainstorming and particularly useful in displaying cause-and-effect relationships.