Probability Management is rethinking uncertainty through communication, calculation, and credible estimates. How many boxes of Girl Scout cookies should a troop purchase for the cookie drive in the face of uncertain demand and available volunteers? Where should an energy firm explore for oil and gas in the face of uncertain geology, prices and environmental concerns? Which investments should we choose for our retirement funds in the face of uncertain markets? Such uncertainties drive decision making at all levels of business, government and personal life, where they are often replaced with single "average" best guesses. Unfortunately this leads to a set of systematic mathematical errors known collectively as the Flaw of Averages, which explain why so many things are behind schedule, beyond budget and below projection.