This paper focuses on many of the issues and problems associated with rough order of magnitude estimating. How do you prepare an estimate when there is very little information on which to base the estimate? While teaching at the University of Chicago, physicist Enrico Fermi had a reputation for asking his students, without any warning, seemingly impossible questions, such as, "how many piano tuners are there in Chicago?"
We face similar conceptual estimating problems everyday in the world of projects. Our management asks for an estimate for a new project using a revolutionary technology never implemented before, and with a larger capacity than has ever been built; and oh, by the way, they need the estimate by tomorrow. This paper is intended to discuss some of the techniques that can be used, as well as some of the problems faced when we are placed in such situations.
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