Decisive: How to Make Better Choices in Life and Work

by Chip Heath

What’s remarkable here is the odd mixture of scientific precision and crude guesstimation. In computing the required strength of an elevator cable, engineers use incredibly sophisticated algorithms and tools. Then, having found the best answer that science has to offer, they take that answer and multiply it by the semiarbitrary number of eleven. It’s like an exercise that a third grader would do in a math workbook. But this crude approach saves lives, and it exhibits an admirable humility: We engineers know that we’ll be prone to overconfidence, and it’s not possible to render ourselves immune to it, so why not just correct for it? The same principle works in less risky contexts as well. Software companies have evolved their own safety factors to pad their project deadlines. Developers at Microsoft, confident in their programming prowess, will often grossly underestimate the amount of time required to reach a goal. So the leaders of the software projects, aware of the developers’ overconfidence, have learned to tack on a “buffer” factor equal to, say, 30% of the schedule.