Complexity:
The sheer number and diversity of assets present in most
industrial undertakings means that it is simply not possible
to develop a complete analytical description of the reliability characteristics of an entire undertaking – or even
any major asset within the undertaking.
This is complicated by the fact that many functional failures are caused not by two or three but by two or three dozen
failure modes. As a result, while it may be fairly easy to
chart the incidence of the functional failures, it is a major
statistical undertaking to isolate and describe the failure
pattern which applies to each of the failure modes. This alone
makes sensible actuarial analysis almost impossible.