> You've never been sure of something only to find out you weren't correct on it?

A 99.9% confidence statement is still wrong 0.1% of the time. If you make one such a day then you ought to be wrong about it once per three years. I don't see that as a problem, of course I get surprised when it happens since it is rare but there isn't much more to it.

And there are even higher levels than 99.9%, many things you are basically never wrong about so we can't find the error bar.

Edit: I think it is good to compare your confidence in a thing to other things. Are you really as confident in this statement as you are in the layman interpretation of 1 + 1 = 2 (ie if you take 1 apple, add 1 apple now you have 2 apples)? Then you can say 100%. But most things are way below that level.

I appreciate that clarification, and yea, with the link I didn't link that I had to choose 100% confident because I would much prefer what you said at 99% or 99.9% confident. I also like what you said about how it brings a surprise because it may be so rare. Thanks for this!

I'd say the questionnaire cheats a bit though since it picks some known common 0.1% cases where most people has to wrong idea. So making statements about a persons confidence and how it relates to the real world based on such questions isn't good science, rather it seems like the purpose was to make the effect seem greater than it is. So maybe me getting reasonable scores was just that I read a lot of forums and have seen data related to common mistakes people do and therefore didn't get tricked by those questions.

Haha good point, yes, I felt a bit hoodwinked on the Borneo question...was feeling so proud of how smart I was until I wasn't :-D