In his opus Thinking, Fast & Slow, Nobel winner Daniel Kahneman (click here for previous post) relates a story from early in his career when he was leading a team to develop a curriculum and write a textbook on judgment and decision-making in high schools. He had assembled a group of experts and after working diligently for a year they had completed an outline of the syllabus and written two chapters. One fine day when discussing procedures for estimating uncertain quantities, it occurred to him that he should get an estimate from everyone on how long he thought this whole project would take. Being the clever psychologist that he was, rather than ask the group to guess publicly, he asked each person to make a confidential prediction. The mean was about two years and the range was about half a year on either side. In other words, the group was very consistent in its prediction.