Sensitivity allows us to reason about the ability of a given measure to discern, by means of simple calculation, one magnitude of displacement from another. The value of sensitivity is affected by uncertainty as well - uncertainty which must be propagated from formulations in §2.
We introduce another index to avoid confusion with , which re-appears once the formulae are expanded. The sensitivity at a point in our new sensitivity plot should be computed as follows:
and are used merely to serve as aliases, which later reduce the complexity (scale) of the equations, making them more digestible.