Confronted with one “True or False” question, an individual has a very small error opportunity space: three. There are three possible responses: true, false, or no answer. “No answer” will always be wrong, a betting man should choose one of the possible answers. But unfortunately situations where the error opportunity space is so narrow are rare. And in the real world, dealing with real problems, these spaces tend to be very large. Note that the size of the error opportunity space, EOS, makes no representations about the consequences of getting the problem right or wrong (or partially right or wrong). When the stock market tanked on May 7th, people involved in that process had a very large EOS. A week out, experts and participants are trying to figure out what went wrong and how to limit similar incidents in the future—they are trying, in effect, to drastically reduce the error opportunity space. This is a job of product designers. By analyzing the goals of the users and the system’s constraining variables, we can come up with conceptual design, interaction design, and interface design that would address the problems that were exposed on May 7th. Coming up with a solution is…