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Error and Reliability

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Most errors are due to flaws in the system rather than a flaw in only ... movement parallax. Psychomotor Skill. Reaction time. stimulus response compatibility ... – PowerPoint PPT presentation

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Title: Error and Reliability


1
Error and Reliability
  • ERROR - an action that violates some tolerance
    limits of a system.

2
Error Reliability
  • Most errors are due to flaws in the system rather
    than a flaw in only the operator.

3
Human Error Probability
  • HEP number of errors per total number of
    opportunities for the error

4
Human Error Categories
  • Error of omission
  • Error of commission
  • Extraneous act - sneeze during operation
  • Sequential Error
  • Time Error

5
The Communication Model
SOURCE
ENCODER
CHANNEL
NOISE
DECODER
DESTINATION
6
Human Reliability Analysis
  • Describe the system goals and functions
  • describe situational characteristics
  • describe personnel characteristics
  • describe tasks and jobs of personnel
  • analyze tasks and jobs to detect situations where
    errors are likely to happen

7
Human Reliability Analysis
  • Estimate the probability that each error will not
    be corrected
  • determine the consequences of each uncorrected
    error
  • devise changes to increase system reliability
  • go back through the previous nine steps and
    evaluate the changes

8
Aural Sensitivity Discriminability
  • Human auditory system is sensitive to a range of
    frequencies 20 - 20 000 hertz
  • highest sensitivity in range 1000 to 3000 hertz
  • discriminate change in frequency as low as 2 hertz

9
Biaural Hearing
  • Having two ears
  • preserves our bilateral symmetry
  • gives us a spare
  • allows us to localise the source of the sound
    stimuli

10
Sound Localisation
  • Inter-aural time difference may be as great as
    660?sec
  • we can detect difference as small as 10 ?sec

11
Visual Sensitivity
  • Depends on prior exposure to some level of
    illumination
  • stimulus of either rods or cones
  • rods more sensitive to light/dark and movement
  • cones more sensitive to colour change

12
Depth Perception
  • The convergence angle of the eyes provides
    potential source of distance data.

13
Monocular Distance Size Cues
  • Interposition - linear perspective
  • movement parallax

14
Psychomotor Skill
  • Reaction time
  • stimulus response compatibility
  • practice and reaction time
  • speed/accuracy trade-off

15
Motor Control
  • Fitts Law states that movement time is a linear
    function of the information generated by
    movement.
  • The two parameters that determine the index of
    difficulty for the movement is the distance from
    the starting point to the centre of the target,
    and the width of the target.
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