Indeed. I wasn't aware of http://en.wikipedia.org/wiki/Wits_and_Wagers. There is no German match for it (yet). I actually considered using a confidence rating but discarded it because it was too easy to game the rules for it - but that was during the first test games that were about estimating your own performance via multiple estimates (called 'strict variant' in the post). When I switched to estimating the range of the other players guesses I didn't reconsider confidence ranges. Could be an interesting variant.

The current gameplay is really simple even though it includes a min-max range. There was a earlier and more complex version that had a 90% range (or more precisely an 1-1/N range) which earned N points if it excluded exactly 1 guess, 1 if it excluded none and 0 if more than 1. That was OK but didn't gain much. The most surprises were still registered by the min-max range.