Page 281 - Six Sigma Demystified

Part 3 s i x s i g m a to o l s 261

TAble T.11 FMEa Occurrence Rankings

Probable Failure Failure Rate C Occurrence
pk
Ranking
Very high >1 in 2 <0.33 10
(inevitable)
1 in 3 0.33 9
High (often) 1 in 8 0.51 8
1 in 20 0.67 7
Moderate 1 in 80 .83 6
(occasional)
1 in 400 1.00 5
1 in 2,000 1.17 4
Low (isolated) 1 in 15,000 1.33 3
Very low 1 in 150,000 1.50 2
Remote (unlikely) <1 in 150,000 >1.67 1

Source: AIAG, 1995.

TAble T.12 Detection-Level Table*
Level Description

10 Nearly certain that failure won’t be detected (p ≈ 1)
9 Extremely poor chance of detection (0.95 < p ≤ 0.99)
8 Poor chance of detection (0.90 < p ≤ 0.95)
7 Highly unlikely to be detected before reaching customer (0.70 < p ≤ 0.90)
6 Unlikely to be detected before reaching customer (0.50 < p ≤ 0.70)
5 Might be detected before reaching customer (0.20 < p ≤ 0.50)
4 Likely to be detected before reaching customer (0.05 < p ≤ 0.20)
3 Low probability of reaching customer without detection (0.01 < p ≤ 0.05)
2 Extremely low probability of reaching customer without detection (0 < p ≤ 0.01)
1 Nearly certain to detect before reaching customer (p ≈ 0)

*FMEA detection levels, from Pyzdek and Keller (2009).