2Reliability Requirements


This chapter is the foundation for the first third of this book dealing with reliability. The chapter covers various uses of the word “reliability” in ordinary conversation and in its specialized uses in engineering. This prepares the way to study reliability requirements. We explore what makes a good reliability requirement and show how appropriate attention to reliability, maintainability, and supportability can create a virtuous circle of improvement and lower cost. Then we move to a more detailed examination of reliability concepts, including reliability effectiveness criteria and figures of merit. This enables us to review some examples of reliability requirements in four areas: products, flow networks, standing services, and on-demand services. The topic of interpretation of reliability requirements is important for proper comparison of performance with requirements, and some examples of comparisons are given here as a preparation for the more detailed coverage of this topic in Chapter 5. We introduce additional figures of merit and some of the statistical procedures that are covered in more detail in Chapter 5. As with all chapters in this book, this chapter closes with a discussion of best practices in creating reliability requirements and a brief summary of key points.


2.2.1 “Reliability” in Conversation

Most people have a good idea of what “reliability” means in ...

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