Except for very simple quantum systems, I wouldn't be able to tell you if uncertainty is in my mind or a consequence of physics.
The weather forecast for November 25 2014 is a 5% chance of rain. Will all future timelines have rain on that day, or is one years long enough to amplify quantum randomness to the scale of global weather patterns? Do you know? I don't know; the physics to determine that is beyond me. Most humans can't distinguish between the two cases when estimating.
All-or-nothing events feel riskier because they indicate a greater chance of catastrophe. A 5% chance of losing your house to a local fire is much better than a 5% chance of losing your house to a city-destroying conflagration. Life insurance claims come steadily; flood insurance claims do not.
"I estimate 5% odds of X happening" can mean at least two things:
* I have about 1-in-20 confidence that all future timelines from this point contain X, and about 19-in-20 confidence that none do.
* I estimate about 1-in-20 future timelines contain X, and 19-in-20 future timelines don't.
Looked at this way, the usual way of quantifying probability seems to be a lot like quantifying area - the first bullet-point by having a 1x20 rectangle, the second by having a 20x1 one. (This also seems valid for having, say, 50% confidence that 1-in-10 future timelines contain X.) It seems like it might be worth having an easy and understandable way to differentiate between these different forms of '5% odds', but any easy way I've been able to think of is barely understandable, and vice versa. Are there any existing standard ways to do this that I'm unaware of? If not, does anyone reading this have any decent answers?
I'm not opposed to coming up with a new word for personal use to help get in the habit of thinking in certain ways; such as bei'e in Lojban to remind myself to think of probability logarithmically. I don't mind doing the same with a word meaning 'such-and-such a fraction of future MWI branches', if that's the best solution, or even just a useful tool; I'd just like to know what the full range of useful approaches really are, first, and any potential loopholes therein or drawbacks thereof.