In this chapter, we have proposed a reliability measures in terms of mean time to failure, availability in terms of mean time between failures, and maintainability in terms of mean time to repair. Are these measures consistent with the definitions presented in this chapter? That is, if reliability, availability, and maintainability are defined as probabilities, will we get the same numbers as if we use the metrics? If not, can one be transformed into the other, or are there basic, irreconcilable differences?