Error Proof and Mistake Proof To Prevent Human Error

Posted by on Jun 7, 2020 in Error Proofing, Mistake Proofing, Poke-yoke | 0 comments

Human error is a huge problem.  It is the third leading cause of death in U.S. hospitals. Researchers estimate that 250,000 people die every year from medical errors in the U.S. alone. Worldwide, human error is the third leading cause of death behind heart disease and cancer.  These are staggering numbers.  In addition to the life and death consequences related to human error, consider all the scrap, rework, and inspection generated by organizations due to human error.

Human error means someone screwed something up and made a mistake.  An error is defined as a fault resulting from defective judgment, deficient knowledge, or carelessness.  It is estimated that the average person will make 773,618 decisions over a lifetime – and will come to regret 143,262 of them. A typical adult makes 27 judgments a day – usually starting with whether to turn off the alarm or hit snooze.

So the question becomes, “how do we reduce the number of errors and mistakes human beings make?”

The answer lies in the mistake, error-proofing, and foolproofing techniques we use to reduce or eliminate them.  These are methods and techniques to make a product, service, or process immune to errors on the part of the user or operator.  They are used to prevent the acceptance or further processing of products, services, or processes when an error or mistake results.

Poke-yoke is a Japanese term that means to mistake-proof a process by building safeguards into the system that prevent or immediately find errors.  A poke-yoke device prevents incorrect parts from being made or assembled and helps us quickly identify a flaw or mistake.

There is a difference between error-proofing and mistake proofing.  Mistake proofing focuses on both the prevention and detection of defects, while error-proofing focuses solely on prevention. Error-proofing breaks the chain of causality so that neither the faulty action nor the resulting error can occur.

Mistake and error-proofing use automatic devices or methods that either makes it impossible for an error to occur or makes the error immediately visible once it has happened.

Many examples of error proofing exist in vehicles we drive: Headlights shut off automatically when left on, or an audible alert is triggered. Car doors do not lock when keys are left inside. Lights on the dashboard appear when tire pressure is low, doors are left open, seat belts are not properly buckled, and turn signals are not shut off.  Sensors indicate other vehicles are passing to prevent blind spots that keep us from seeing them.  These devices help prevent many accidents that otherwise may have occurred.

Mistake proofing techniques can be applied in the following situations:

  • In a process step where potential human error can cause mistakes or defects to occur primarily in processes that rely on the worker’s attention, skill, or experience.
  • In a service where the customer can make an error that affects the outcome of the service.
  • At a process step hand-off, where output is transferred from one worker to another worker or to another functional area.
  • When a minor error created early in a process can cause significant problems later.
  • When the consequences of making an error or mistake are expensive or dangerous.

The following steps can be taken to mistake-proof a process.

  1. First, map the process and try to determine where and when errors are likely to be made.
  2. Next, try to determine the source of each potential error.
  3. Then, for each potential error, consider using the following techniques to prevent it.
    • Elimination:  try to eliminate the step that is causing the error.
    • Replacement:  if you cannot eliminate the step causing the error, try to replace it with an error-proofed one.
    • Facilitation:  try to make the correct action to prevent the error easier than making the error.
  4. If making the error is impossible, try to think of ways to detect the failure and minimize its effects.

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