Similar Equipment Method
The primary objective of prediction during the early stages of a project (i.e., preliminary study, feasibility study, early project definition) is to provide quantitative estimates of reliability that can be used to:
Compare design options.
Establish realistic reliability targets.
Identify areas of high risk.
Provide inputs to trade off studies.
In general, such predictions will be concerned mainly with assessments at system and sub-system level and, because information is limited during early stages, will usually involve a considerable degree of engineering judgement.