An Iterative Estimation Technique: Wideband Modified DelphiThis method was introduced by Barry Boehm in the 1970s, [4] and it has spawned several variants. It is often referred to as the Wideband Modified Delphi . The principle is to bring several heads together on an issue and try to reach a consensus. When these "heads" used are the actual development team, this approach is more likely to get their commitment than would random numbers raining from above. This is roughly how it works:
As the phase or iteration unrolls, actual data is then collected for these tasks and is used in the next estimate. At the next round (the next iteration, for example), when it is time to do another estimation, the previous estimates and the actual numbers are given to the participants, to help them adjust their natural optimism or pessimism. There are plenty of variants and refinements, as you can imagine. You could iterate on steps 5 and 6 (although it is often not necessary). You can choose an informal route, using e-mail or simply walking from cubicle to cubicle with a notepad to discuss planning hypotheses with the people who had given great variance. You can do it very formally , using templates and tools to compute ranges and uncertainties, even using Monte Carlo simulations to generate a probability distribution of possible estimate outcomes based on the final estimate values. See Wiegers 2000 for another, more detailed description of this Wideband Delphi estimation technique. |