I don't use a formal risk assessment method and instead make a reasoned guess and then make a judgement call.
Conceptually it would be an interesting exercise to establish the risk parameters and develop some software that would provide a go/no go decision. Only problem I forsee is that it would always say NO!
I suspect that if your question is as a result of anything other than idle curiousity then you may wish to consider whether flying is really for you as you should be in a permanent state of risk analysis/decision making/review. If you ever feel that you're not in this loop at any stage of a flight....then maybe you should re-evaluate the situation :-)