Occurrence Rating Scale (Should be tailored to meet the needs of your company) Rating Description Potential Failure Rate Very high: More than one occurrence per day or a Failure is 10 probability of more than three almost occurrences in 10 events (Cpk < 0.33) inevitable One occurrence every three to four days High: Failures or a probability of three occurrences in 9 occur almost 10 events (Cpk ≈ 0.33) as often as not High: One occurrence per week or a probability 8 of 5 occurrences in 100 events (Cpk ≈ Repeated failures 0.67) High: Failures One occurrence every month or one 7 occur often occurrence in 100 events (Cpk ≈ 0.83) Moderately One occurrence every three months or 6 three occurrences in 1,000 events (Cpk high: Frequent failures ≈ 1.00) Moderate: One occurrence every six months to one 5 Occasional year or five occurrences in 10,000 events (Cpk ≈ 1.17) failures Moderately One occurrence per year or six low: 4 occurrences in 100,000 events (Cpk ≈ Infrequent 1.33) failures Low: One occurrence every one to three years 3 or six occurrences in ten million events Relatively few failures (Cpk ≈ 1.67) Low: Failures One occurrence every three to five years 2 are few and far or 2 occurrences in one billion events between (Cpk ≈ 2.00) One occurrence in greater than five Remote: 1 Failure is years or less than two occurrences in unlikely one billion events (Cpk > 2.00)
Occurrence Rating Scale (Should be tailored to meet the needs of your company) Rating Description Potential Failure Rate 10 Very high: Failure is almost inevitable More than one occurrence per day or a probability of more than three occurrences in 10 events (Cpk < 0.33) 9 High: Failures occur almost as often as not One occurrence every three to four days or a probability of three occurrences in 10 events (Cpk ≈ 0.33) 8 High: Repeated failures One occurrence per week or a probability of 5 occurrences in 100 events (Cpk ≈ 0.67) 7 High: Failures occur often One occurrence every month or one occurrence in 100 events (Cpk ≈ 0.83) 6 Moderately high: Frequent failures One occurrence every three months or three occurrences in 1,000 events (Cpk ≈ 1.00) 5 Moderate: Occasional failures One occurrence every six months to one year or five occurrences in 10,000 events (Cpk ≈ 1.17) 4 Moderately low: Infrequent failures One occurrence per year or six occurrences in 100,000 events (Cpk ≈ 1.33) 3 Low: Relatively few failures One occurrence every one to three years or six occurrences in ten million events (Cpk ≈ 1.67) 2 Low: Failures are few and far between One occurrence every three to five years or 2 occurrences in one billion events (Cpk ≈ 2.00) 1 Remote: Failure is unlikely One occurrence in greater than five years or less than two occurrences in one billion events (Cpk > 2.00)
FMEA-Scales-v3.docx