1. Mistake Proofing and Poka Yoke http://www.managementsupport.com

2. Outline What is Mistake Proofing? Everyday Examples
Effectiveness & ROI
Error Proofing and SPC
Inspection Techniques
Types of Poka Yokes

3. Everyday Examples
3.5 inch diskettes cannot be inserted unless diskette
is oriented correctly. This is as far as a disk can be inserted upside-down. The beveled corner of the diskette along with the fact that the diskette is not square, prohibit incorrect orientation.
Fueling area of car has three error-proofing devices:
1. insert keeps leaded-fuel nozzle from being inserted
2. tether does not allow loss of gas cap
3. gas cap has ratchet to signal proper tightness and
prevent overtightening.
PARAPHRASE SLIDE
ask for more car examples.
New lawn mowers are required to have a safety bar on the handle that must be pulled back in order to start the engine. If you let go
of the safety bar, the mower blade stops in 3 seconds or less.

4. Poka yoke & SPC

5. Individually, mistakes are rare
Task Type Probability
Detection of deviation or inspection 0.07
Alpha input per character
Numeric input per character
Assembly per task element
As a group they are common
Research study #1 (Harris) >0.80
Research study #2 (Rook)
Research study #3 (Voegtlen)
Research study #4 (Headlamps) >0.70
NASA mishaps >0.50
FAA Maintenance problems >0.94
At the start of this presentation we said that individual errors were rare events. This is shown by the data above
Here are some human error rate data. You’ll notice that the error rates differ for each task type. Notice that the more routine tasks are performed more reliably.
Does this data suggest we should spend our time addressing knowledge-based mistakes (since they are more likely at any given opportunity)? No, workers experience far more opportunities to make skill-based errors. The number of opportunities to make an error performing skill-based actions far exceeds the number of opportunities to make knowledge-based errors.
Data from “Human Reliability Data - The State of the Art and the Possibilities”
Jeremy C. Williams, 1989 CEGB