It is easy enough for managers to see that things in the business world vary. Some marketing campaigns produce great results; similar ones do not. There are times when the supply chain works effortlessly, and other times when every step is snarled. Some days the numbers look fine, and other days they just don’t add up. Variation is a manager’s natural enemy, making it more difficult to sort out what’s really going on, make valid predictions, and be in control.