Description: The Ellsberg paradox is a paradox in decision theory and experimental economics in which people's choices violate the expected utility hypothesis. One interpretation is that expected utility theory does not properly describe actual human choices. It is generally taken to be evidence for ambiguity aversion. The paradox was popularized by Daniel Ellsberg, although a version of it was noted considerably earlier by John Maynard Keynes. Ellsberg raised two problems: 1 urn problem and 2 urn problem. Here, 1 urn problem is described, which is the better known one.