Defect Removal Effectiveness

The concept of defect removal effectiveness and its measurement are central to software development. Defect removal is one of the top expenses in any software project and it greatly affects schedules. Effective defect removal can lead to reductions in the development cycle time and good product quality. For improvements in quality, productivity, and cost, as well as schedule, it is important to use better defect prevention and removal technologies to maximize the effectiveness of the project. It is important for all projects and development organizations to measure the effectiveness of their defect removal processes.

In Chapter 4 we briefly touched on the metrics of defect removal effectiveness and fault containment. In this chapter we elaborate on the concept, its measurements, and its use in the phase-based defect removal model. After a brief literature review, we take a closer look at the defect injection and removal activities of the phases of a typical development process. Using a matrix approach to cross-tabulate defect data in terms of defect origin and phase of defect discovery (where found), we provide a detailed example of calculating the values of the overall defect removal effectiveness, the inspection effectiveness, the test effectiveness as well as the phase-specific defect removal effectiveness. We then establish the formulas of these indexes based on the defect origin/where found matrix. Next we elaborate the role of defect removal effectiveness in quality planning with more examples. We discuss the cost effectiveness of phase defect removal and also the defect removal effectiveness levels in the context of the capability maturity model (CMM) before summarizing the chapter.

Before we begin, a point on terminology is in order. Some writers use the terms defect removal efficiency, error detection efficiency, fault containment, defect removal effectiveness , and the like. In this book we prefer the term effectiveness rather than efficiency . Efficiency implies the element of time, effectiveness is related to the extent of impact and we think the latter is more appropriate. In the following sections we may sometimes use the two terms interchangeably, especially when we refer to the definitions and metrics of other writers.