Human Error and Biases

1. Human Error and Biases

2. Human Error - Definition • An inappropriate or undesirable human decision or behavior that reduces, or has the potential for reducing, effectiveness, safety, or system performance. • An undesirable effect or potential effect on systems or people. • An error that is corrected before it can cause damage is an error nonetheless.

3. Error ClassificationDiscrete Action • Omission - Forgetting to do something, or just deliberately ignoring it. • Commission - Performing an act incorrectly. • Sequence - Right action, wrong order. • Timing / Rate -Too fast or too slow.

4. Error ClassificationInformation Processing • Specific error categories at each stage of information processing. • 1. Observation of system state • 2. Choice of hypothesis • 3. Testing of hypothesis • 4. Choice of goal • 5. Choice of procedure • 6. Execution of procedure

5. Error ClassificationInformation Processing - continued • The errors depend on the level of behavior. • 1. Skill-based behavior • 2. Rule-based behavior • 3. Knowledge-based behavior

6. Error ReductionSelection • Selection of personnel with skills and capabilities (perceptual, intellectual, motor skills, etc.) • Limitations • 1. Not easy to determine skills required. • 2. Few reliable tests for measuring skill levels. • 3. Limited supply of qualified people.

7. Error ReductionTraining • Proper training of personnel reduces errors. • Limitations • Old habits are hard to break. • Training can be expensive.

8. Error ReductionDesign • Exclusion • Particular errors made impossible to commit • Prevention • Particular errors made difficult to commit • Fail-safe • Consequences of errors reduced in severity

9. Human Biases • People give an undue amount of weight to earlyevidence or information. • Humans are generally conservative and do notextract as much information from sources asthey optimally should. • The subjective odds in favor of one alternative orthe other are not assessed to be as extreme orgiven as much confidence as optimally they should.

10. Human Biases - continued • As more information is gathered, people becomemore confident in their decisions,but not necessarily more accurate. • Humans have a tendency to seek far moreinformation than they can absorb adequately. • People often treat all information as if it wereequally reliable.

11. Human Biases - continued • People cannot entertain more than a few(three or four) hypotheses at a time. • People tend to focus on only a few criticalattributes at a time and consider only abouttwo to four possible choices that are rankedhighest of those few critical attributes. • People tend to seek information that confirmsthe chosen course of action and to avoidinformation or tests whose outcome coulddisconfirm the choice. (Confirmation Bias)

12. Human Biases - continued • A potential loss is viewed as having greater valuethan a gain of the same amount. (Risk Aversion) • People believe that mildly positive outcomes are more likely than either mildly negative or highly positive outcomes. • People tend to believe that highly negative outcomes are less likely than mildly negative outcomes.