1ISE 311 Ch. 19

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

9ISE 311 Ch. 19

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.

11ISE 311 Ch. 19

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: Don’t 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.

19ISE 311 Ch. 19

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.

20ISE 311 Ch. 19

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.