3. Service-Oriented FMEA
3.1 Risk and the Risk Priority Number of FMEA
In the traditional FMEA, the risk priority number (RPN) is calculated by the multiplication of three
risk factors, severity, occurrence and detection, and each factor can be described as the following [18]:
1) Severity (S): Result generated from failure
2) Occurrence (O): Opportunity or probability of a failure
3) Detection (D): Opportunity for an unidentified failure because of the difficulty in detection
The traditional risk prioritization ignores that three factors may have different weights in system,
and especially occurrence is a key factor in non-repairable system. Patrick et al. [18] emphasize that the
severity and the occurrence are two key items which should be used in FMEA priority analysis rather
than the item of the detection.
A service failure in service industries is a problematic outcome causing significant damage to
customer satisfaction [19, 20, 21]. The RPN of FMEA is used to identify potential failures before they
occur to minimize the risk associated with them. However, some researchers have been raised different
views on the appropriateness of the RPN [17].
The notion of risk has both uncertainty and some kind of loss or damage that might be received.
The risk is understood to someone as a subjective thing, because a risk depends on who are looking
[22]. In analyzing risk, we are attempting to envision how the future will turn out if we undertake a
certain course of action. Fundamentally, a risk analysis consists of an answer to the following three
questions: