Monday, July 18, 2016

Sixteen Human Error Modes for Mistake Proofing


We all make mistakes, to err is human.  The question is why does it happen and how can you prevent it.  The essence of mistake-proofing is to design both products and processes so that human errors or mistakes are impossible to make or, at the least, they are easy and early to detect and correct. Poka-yoke is Japanese slang for mistake-proofing, a term coined by Shigeo Shingo.

When performing a mistake-proofing analysis on a manufacturing, service or business process, it is of course important to identify every human error possible during each process step. There are 16 human error modes particularly helpful to understand when identifying potential human errors.

The Sixteen Human Error Modes

1.     Omission
What part of the process is prone to be omitted?

2.     Excessive/Insufficient Repetition
What part of the process is prone to be excessively repeated?

3.     Wrong Order or Sequence
In what wrong sequence can the process be executed?

4.     Early/Late Execution
What execution can be early or late?

5.     Execution of Restricted Work
What tasks could be executed by unauthorized personnel?

6.     Incorrect Selection (or Identification)
What object of the process is prone to be incorrectly selected or identified?

7.     Incorrect Counting (or Calculating)
What objects of the process can be counted, measured, or calculated incorrectly?

8.     Misrecognition (or Misunderstanding or Misreading)
What misunderstanding or misreading is prone to occur?
What information, risk, or failure/error is prone to be overlooked?
What miscommunication is prone to occur?
What incorrect decision is prone to occur?

9.     Failing to Sense Danger
What information, risk, or failure/error is prone to be overlooked?

10.  Incorrect Holding
What object of the process are prone to mishandling?

11.  Incorrect Positioning
What positioning setting error is prone to occur?

12.  Incorrect Orientation
What orientation error is prone to occur?

13.  Incorrect Motion
What motion or movement error is prone to occur?

14.  Improper Holding
What object of the process are prone to mishandling?

15.  Inaccurate Motion
What motion or movement error is prone to occur?

16.  Insufficient Avoidance
What can be unintentionally touched, stuck, or splashed?
What movement can cause harm?

We must approach human error by considering the interfaces of the process that the operator is engaged in. The process should be designed to permit communication between the process and the operator.

Shingo argued that errors are inevitable in any manufacturing process, but that if appropriate Poka-yokes are implemented, then mistakes can be caught quickly and prevented from resulting in defects. By eliminating defects at the source, the cost of mistakes within a company is reduced.


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