Design errors and some upsets are not statistically predictable and can cross redundancy boundaries as common mode faults, so redundancy management and assessment methods should be chosen to preclude or mitigate common mode faults and upset effects where needed. Qualitative methods (fault tree analysis, common mode analysis, functional FMEA) can show the possible effects of design errors and upsets, how they are precluded or mitigated, and can be used iteratively to judge the assurance the chosen strategies achieve.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.