Wonder if I articulate this as half coherently as possible to enable someone out there to assist…

I’d like to write create a calculation that will work out whether a safety measure is adequately reasonable or not based on the cost of an accident and the cost of the mitigation measure. This would be based on three factors: the cost of a serious accident – which would be a fixed figure, i.e. let’s say for the sake of the equation this would be 5000, the cost of the mitigation measure which will be variable depending on what it is, and finally the probability of that accident happening over the lifespan of a bit of work, which would also be variable.

I know that’s little information, but does anyone get the gist of what I’m on about and how such a formula might look?