Chapter 17: Error Reduction

1. Chapter 17: 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

2. 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

3. Causes of errors • Poor design of equipment • Poor management of equipment • Poor procedures • Poor training • Other factors

4. 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.

5. 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.

6. Types • 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

7. Error analysis techniques • Checklists • FMEA / FMECA • Decision structure tables • Fish diagrams • Fault trees

8. 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

9. 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.

10. 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.

11. 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.

12. 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.

13. 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.

14. 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.

15. 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.

16. 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.

17. 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.

18. 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.

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.

20. 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.