During the feasibility and early project definition stages of a project, predictions obviously cannot be based on detailed design information. In spite of this, major decisions are made and large-scale funding is committed at this time. It is at this stage that accurate predictions would be most valuable.

It is an unfortunate fact, therefore, that the greatest uncertainty is attached to predictions during the early stages of design. Despite this, the best available methods must be employed to identify critical design areas as early as possible. Examples of such methods include comparison with similar equipment and generic parts count assessments. Such methods are described more fully in Reliability Prediction Methods.