Fred was admitted to a hospital for a cerebral aneurysm surgery. Just before the operation, a worried Fred asked the doctor, "I heard this operation is highly risky. What are my chances of survival?"
The Surgeon replied: "I'm absolutely positive that you will survive the operation."
Fred, a little relieved, but still in doubt, asked, "How can you be so sure?"
The Surgeon said, "Four out of five patients die in this operation, and last week, my fourth patient died."