Chapter 19: Error Reduction

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Chapter 19 Error Reduction

• ERROR An event when an action other than
  desired takes place.
• Sequence
• Consider accidents to be predictable and
  preventable.
• i.e., break the sequence

Normality ? error ? accident ? minor loss ? major
loss ? catastrophe
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Error reduction ? cognitive ergonomics.

• Justifications of ergonomics center around
• Reduction of physical stress
• Reduction of errors (waste)
• Benefits of reducing errors
• Improves safety
• Improves quality
• Improves productivity

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Causes of Errors

• Poor design of equipment
• Poor management of equipment
• Poor procedures
• Poor training
• Other factors

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Errors in the Workplace

• Costs
• Range from seconds of time to injury and death.
• Include cleanup, fines, loss of market share,
  legal costs.
• Are difficult to quantify.
• Are often concealed.
• Are perceived unequally.

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Errors in the Workplace

• Reduce costs by
• Give more attention to problems where potential
  cost is higher.
• Be a scientist, not an advocate.
• Seek root causes, not blame.
• Avoid punishment.

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Types of Errors

• Omission or commission
• Type 1 or Type 2
• System or measurement (of the system)
• Observed error System Measurement
• Perception, decision, or action
• Slip vs mistake
• Slip non-deliberate failure to follow rule
• Mistake
• Conscious planning results in unanticipated
  action
• Failure of knowledge
• Malice deliberate violation of rules or
  procedures

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Error Analysis Techniques

• Checklists
• FMEA / FMECA
• Decision structure tables
• Fish diagrams
• Fault trees

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Making Decisions/Actions in Public

• Eliminating privacy can eliminate many errors.
• Add lighting or move objects/people to visible
  places.
• Require approval for deviations from policy.
• Increase the number of required decision makers.
• Decisions tend to be slower but better quality.
• Exceptions
• Emergency situations
• High risk environments

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Guideline 1 Get Enough Information

• Generate relevant information.
• May be difficult if information is subjective.
• Provide additional information for novices.
• Ensure information reception.
• Be sure people know how to get and use
  information.
• Be sure novices know how to find it.

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Guideline 2 Ensure That Information Is Understood

• Communicating with the general public is more
  difficult than with employees.
• For directions, use a series of signs instead of
  maps.
• For maps, use track up rather than north.
• Translate and standardize words.
• Avoid double negatives.
• Field-test procedures.
• Use information feedback.

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Guideline 3 Have Proper Equipment /
Procedures / Skill

• Equipment
• Design
• Amount
• Arrangement
• Maintenance
• Procedures
• Computer procedures
• Human procedures

• Skill
• Consider skill of machine vs. person.
• Do not assume a fully capable and trained
  operator.
• Provide job aids and refresher training.
• Novices make more errors than experienced
  operators.

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Guideline 4 Dont Forget

• Reduce the need to remember.
• Avoid verbal orders.
• Make a list.
• Do it now.
• Have standard places for things.
• Use memory aids.
• Make them complete, convenient, and accessible.
• Use forms to indicate when information is
  missing.
• Consider downsides.
• Create a pattern or standard sequence.
• Use calendars, appointment cards, and reminders.

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Guideline 5 Simplify the Task

• Improve communication.
• Field-test instructions.
• Use all-letter or all-numeric codes.
• Avoid complex words.
• Emphasize important information.
• Let the operator filter information.

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Guideline 6 Allow Enough Time

• Too little time results in stress and errors.
• Time stress is one stress than can be reduced.
• Assign additional staff when necessary.
• Cross-train employees to provide flexibility.

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Guideline 7 Have Sufficient Motivation
/Attention

• Motivation
• Motivation is not a substitute for engineering.
• Social pressure can help or hinder performance.
• What motivates people is not always obvious.
• Attention
• Lack of sleep and substance abuse may cause
  lapses.
• For critical decisions and actions, minimize
  distractions.

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Guideline 8 Give Immediate Feedback

• Calibrate instruments periodically.
• Use closed-loop systems.
• Notify the operator when an error has been
  corrected.
• Make error messages specific and understandable.
• Consider that operators may disable alarms.
• Reduce delay between error and detection.

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Error Message Guidelines

• Try to reduce or eliminate the need for them.
• Be specific and precise.
• Be positive and constructive.
• Be consistent in language use and display format.
• Use user-centered phrasing.
• Test their usability.

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Guideline 9 Improve Error Detectability

• Amplify the signal
• Match it to enable paired comparison.
• Do not contradict population stereotypes.
• Consider location and time.
• Reduce the noise.

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Guideline 10 Minimize Consequences of
Errors

• Make important decisions or actions multi-step
  and reversible.
• Make equipment and procedures fail-safe.
• Consider ease of recovery.
• Ensure recovery does not cause additional
  problems.
• Minimize spread of the error through the system.
• Provide guards.

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Inspection

• Can be manual, fully automatic, or semiautomatic.
• Inspect all items for one characteristic at a
  time.
• For searches, consider task, environment, and
  personnel factors.
• Train inspectors and provide an inspection
  manual.
• Inspection Workstations
• Consider replacing microscopes with video
  cameras.
• Use an appropriate colored background.
• Make chair, work surface, and lighting adjustable.