Occurrence

Occurrence ( O ) : Occurrence is the likelihood that a specific cause/mechanism of failure will occur.The likelihood of occurrence ranking number has relative meaning rather than an absolute value.Preventing or controlling the causes/mechanisms of failure through a design or process change is the only way a reduction in the occurrence ranking can be effected.

Table 2. Suggested Process Failure ‘s Occurrence Evaluation Criteria

Probability	Likely Failure Rates	Ranking
Very High : Persistent Failures	≥ 100 per thousand pieces	10
	50 per thousand pieces	9
High : Frequent Failures	20 per thousand pieces	8
	10 per thousand pieces	7
Moderate: Occasional Failures	5 per thousand pieces	6
	2 per thousand pieces	5
Low: Relatively Few Failures	1 per thousand pieces	4
	0.5 per thousand pieces	3
Remote:Failure is Unlikely	0.1 per thousand pieces	2
	≤0.01 per thousand pieces	1

Articles from FMEA Third Edition DaimlerChrysler Corporation, Ford Motor Company, General Motors Corporation.