Nine in Ten
A table game for three to eight people of any age. Each question has an answer somewhere in the room. On paper, everyone writes a low and a high they are nine-in-ten sure the answer sits between. Then you get up and count.
If your ranges are right, about nine of ten will catch the answer. Most people catch fewer the first time, and widen their ranges in the second round. Nobody has an advantage, because nobody knows the answers.
Playing alone? Today's Guess is one question a day with the same nine-in-ten range. The idea behind it is in Thinking in Odds.