Much of what a CFO does can rightly be described as science: numbers, spreadsheets and reports all live in the empirical, analytical realm of cold, hard facts. While much of accounting does involve making assumptions, there is one part of the CFO's job description that might more accurately be described as art than science. 

Managing analysts' expectations is about color, texture, and the chiaroscuro of suggestion, mandated, of course by the rules that govern fair dealing and access to information. Yet research released recently by McKinsey shows that over the past 25 years, analysts' expectations have been consistently over optimistic, especially when it comes to earnings forecasts.

Federal Reserve Chairman Ben Bernanke could not have been clearer when he said that interest rates would remain "exceptionally low" for "an extended period" at a congressional hearing this week. In Fed speak, that counts as clarity.