"Programmers seem to be a bit more productive after they’ve done the estimate themselves, compared to cases in which the manager did it without even consulting them." (Tom DeMarco & Timothy Lister, "Peopleware: Productive Projects and Teams", 1987)
"[The common definition of estimate is] 'the most optimistic prediction that has a non-zero probability of coming true' [...] Accepting this definition leads irrevocably toward a method called what's-the-earliest-date-by-which-you-can't-prove-you-won't-be-finished estimating" (Tom DeMarco & Timothy Lister, "Peopleware: Productive Projects and Teams", 1987)
"Because one has to be an optimist to begin an ambitious project, it is not surprising that underestimation of completion time is the norm." (Fernando J Corbató, "On Building Systems That Will Fail", 1991)
"[…] all activities are probabilistic, not deterministic! There is a probability that a task can be completed in a certain time, given a fixed level of effort. If you want to guarantee that the task is finished in a fixed time period, then you must vary effort, reduce scope, or sacrifice quality. You can’t have it all. Therefore, an exact estimate is an oxymoron." (James P Lewis, "Project Planning, Scheduling, and Control" 3rd Ed., 2001)
"Be sure you understand whether you're presenting uncertainty in an estimate or uncertainty that affects your ability to meet a commitment." (Steve McConnell, "Software Estimation: Demystifying the Black Art", 2006)
"Don't expect better estimation practices alone to provide more accurate estimates for chaotic projects. You can't accurately estimate an out-of-control process." (Steve McConnell, "Software Estimation: Demystifying the Black Art", 2006)
"Don't intentionally underestimate. The penalty for underestimation is more severe than the penalty for overestimation. Address concerns about overestimation through planning and control, not by biasing your estimates." (Steve McConnell, "Software Estimation: Demystifying the Black Art", 2006)
"Not all estimation methods are equal. When looking for convergence or spread among estimates, give more weight to the techniques that tend to produce the most accurate results." (Steve McConnell, "Software Estimation: Demystifying the Black Art", 2006)
"The primary purpose of software estimation is not to predict
a project's outcome; it is to determine whether a project's targets are
realistic enough to allow the project to be controlled to meet them." (Steve
McConnell, "Software Estimation: Demystifying the Black Art", 2006)
"Treat estimation discussions as problem solving, not negotiation. Recognize that all project stakeholders are on the same side of the table. Everyone wins, or everyone loses." (Steve McConnell, "Software Estimation: Demystifying the Black Art", 2006)
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