Chapter 4, “Reliability Requirements, Modeling, and Allocation,” takes a deep dive into developing reliability requirements and allocation. It starts by defining common metrics and their applications. It then continues by exploring required inputs for developing reliability requirements that may be based on voices of business or their customers. These requirements may be also be based on use and operational profiles or even the product’s mission. Another aspect of developing reliability requirements is to review and quantify failures of fielded and predicate devices. The activities to define reliability requirements based on voices of business and customer along with inherent reliabilities of predicate devices enables the design team to identify reliability gaps. The design and reliability teams can then design and plan component testing based on the known gaps.