Richard P. Feynman, the late theoretical physicist, spoke about being fooled by numbers. He famously said: "The first principle is that you must not fool yourself and you are the easiest person to fool." Numbers can also be scary. Many people avoid discussing numbers, which calls to mind a quotation from Mark Twain: "It is better to keep your mouth closed and to let people think you are a fool than to open it and remove all doubt."

On this thread I want you to discuss with your classmates two things: 1) Times when you made mistakes with numbers, and 2) Times when numbers scared you (Please, ignore Twain's advice).

Let me start by telling you about a conversation I had with my friend Roger Stone. No, not the criminal Trump pardoned. My friend is a smart guy. Undergraduate degree from Yale and an MBA from Columbia. This conversation happened nearly 20 years ago over lunch. I had just received word that my landlord was going to convert my apartment building. Tenants would be allowed to buy their apartments and then sell them for a profit. I started to review the numbers for the first time with Roger. Roger began to laugh. He then told me that my numbers were wrong because I failed to incorporate the "cost of goods"the price of the apartment in my calculation. Oops. A foolish mistake. Roger then told me about his own foolish mistake. As a young product manager at Bristol-Myers, he developed a promotion, but forgot to account for the cost of goods in his pay-out analysis.