What seems to be taking shape while doing this is the idea of the player having access to a tool, mostly separated from the rest of the game, to help calculate probabilities. It would allow new (possible) facts to be entered with priors, facts split up into conjunctions, dependencies noted between facts and so on. The tool would then calculate probabilities for you while you tweak the calculation. (Possibly color coded or otherwise abstracted if we expect numbers to be seen as scary.)

I'm not even gonna try to do make this into an intuitive or full featured tool right away, but in a final release I would imagine a very polished interface with drag&drop graphs for dependencies, folding to hide irrelevant details etc.

Early on in the game, there would be heavy prompting on exactly how to use the tool while later on the player would be left increasingly on their own in figuring out how to enter statements and facts she encounters.

First of all, is this in line with what other people are envisioning?

Secondly, this seems like something which may actually be useful in real life as well (and I could see the game ending with an encouragement to do just that). Does anyone know of such a tool which already exists? If nothing else, it might be good for salvaging ideas from. Some quick Googling doesn't reveal anything beyond simple tools where you can put in the numbers for a single equation and tools special fitted for a single application.

Edit: Argument Map software seem to be what I was looking for.