With this sort of thing, or anything really, you either use bulletproof mathematical models derived from first principles (or empirically) with calibrated real quantities, or you wing it intuitively using your built-in hardware. You do not use "math" on uncalibrated pseudo-quantities; that just tricks you into overriding your intuition for something with no correct basis.

This is why you never use explicit probabilities that aren't either empirically determined or calculated theoretically.

This is a very good general point, one that I natively seem to grasp, but even so I'd appreciate it if you wrote a top-level post about it.