Cone of Uncertainty

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The Cone of Uncertainty describes the course of uncertainties in a project . It goes back to a study by NASA , which found that an estimate that was made at the beginning of the project life cycle (i.e. before the requirements phase) is still burdened with an average uncertainty of factor 4. For example, the "actually" required time for a project can be four times as long or only a quarter as long as originally estimated.

This factor differs depending on the nature of the project: the greater the proportion of research and development, the greater the uncertainty.

The uncertainty steadily decreases in the course of the project, but only reaches 0% at the end of the project. The name "Cone of Uncertainty" is derived from the course of the uncertainty curve, which initially falls sharply and then gradually approaches 0.

Consequences from the Cone of Uncertainty:

  • An estimate of time, costs and quality at the beginning of the project can only provide a rough guide
  • Estimates for the creation of a project plan and thus also the project plan itself should be updated regularly
  • Uncertainties can be incorporated directly into the estimates (see two-time method , three-time method )
  • If possible, the project plan should contain and reflect the uncertainties