1. A system for implementing a top-down flow down of at least one system requirement to allocate variability to system components such that overall system response meets the at least one system requirement, comprising: a processor circuit having a processor and a memory; and an allocation system stored in the memory and executable by the processor, the allocation system including logic that accepts a target value for the system response; and logic that uses a non-linear model of the system to relate response variable values to targeted variable values and targeted mean values of the response variable values.