The first step in the design process is to translate the overall system reliability requirement into reliability requirements for each of the subsystems. This process is known as reliability allocation. The allocation of system reliability involves solving the basic inequality:

where

is the is the allocation reliability parameter for the i^{th} subsystem

R* is the system reliability requirement parameter

f is the functional relationship between subsystem and system

reliability

For a simple series system in which the R’s represent probability of

survival for t hours, the above equation becomes