Cone of Uncertainty

The Cone of Uncertainty describes the course of uncertainties in a project. It goes back to a study of NASA, who has determined that an estimate that was ( even before the requirements phase ) made ​​at the inception of the project life cycle, is still charged on average with an uncertainty of a factor of 4. For example, four times as long, or even a quarter of his " real " time required of a project as long as originally estimated.

This factor varies depending on the nature of the project, the larger the share of research and development is, the higher the uncertainty.

The uncertainty increases steadily during the project, but only achieved with the project ends 0%. The name " Cone of Uncertainty" is derived from the first significant drop and then gradually approaching 0 the course of the uncertainties curve from.

Consequences of the Cone of Uncertainty:

  • An estimate of time, cost and quality at the beginning of the project can at best provide a rough guide
  • Estimates in the preparation of a project plan and therefore the project plan itself should be updated regularly
  • Uncertainties can be directly incorporated into the estimates (see two-time method, three-time method)
  • If possible, the project plan should include and reflect the uncertainties
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