0 7 4 0 -7 4 5 9 / 0 5 / $ 2 0 . 0 0 © 2 0 0 5 I E E E M a y / J u n e 2 0 0 5 I E E E S O F T W A R E 5 7 focus A software development team estimating the effort needed to complete a complex project divided it into activities, estimated the effort required for each, and eventually arrived at a total of about 17,000 work hours-20,000 maximum, 15,000 minimum. Then the team leader asked a member with considerable domain expertise what his experience had been on similar software projects. "I

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... spending at least 40,000 work hours," the developer said. "Even then, about 25 percent of them failed completely. In all projects, more than 50 percent of the effort was due to unexpected events."