Term
| Measurement and Assessment of manual lifting |
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Definition
Biomechanical
Physiological
Psychophysical |
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Term
| Factors affecting lifting ability |
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Definition
Task:
-weight, height of lift
-frequency of lift
-load distance from body
-load distance from floor(bending)
-load position relative to sagittal plane(twisting)
-C.M. of load
-load dimension and characteristics
-handles
-lifting technique
Personal:
-strength
-body size
-experience and knowledge of task
-attitude
Environmental:
-floor conditions(traction, plane)
-vibration
-illumination
-heat and cold
Management:
-frequency and length of rest breaks
-variability of tasks(job rotation or enrichment)
-overtime
Psychosocial:
-attitude to work
-interaction with coworkers |
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Term
| Most efficient lift range and weight |
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Definition
| 40-60 inches off floor and about 40 lbs |
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Term
| Scientific guides for protection from injuries |
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Definition
-The NIOSH lifting equation
-The Job Severity Index(Texas Tech) |
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Term
Biomechanical Measurement and Assessment
(limits) |
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Definition
This criterion is for infrequent, heavy lifts
-Compressive forces over 6400N at the L5/S1 disc is considered dangerous
-3400-6400N is considered a range which injury is likely to occur
-Below 3400N is considered safe |
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Term
| Psychophysical measurement and assessment |
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Definition
Determines the max acceptable lifting weight(MAL)
MAL-the max weight a worker is willing to lift and is capable of lifting for a shift, at work |
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Term
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Definition
9.5 kcal/min for 8hr jobs
-50% of the person's PWC(VO2 Max) for 1hr
-40% for 1-2hrs
-33% for 2-8hrs |
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Term
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Definition
Computes a RWL based on a constant factor LC adjusted for 6 work variable(multipliers). Biomechanical, metabolic, and psychological criteria in the form of one equation.
HM-distance of the person from load
VM-Height of the object at the start of the lift
DM-Vertical range of the lift
AM-Amount the upper body is twisted
FM-Frequency-duration-range of lift combo
CM-How good the handle coupling is |
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Term
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Definition
LI=L/RWL
if LI > 3 the work is at great risk to injury |
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Term
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Definition
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Term
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Definition
the amount of information uncertainty required to decide between two equally likely alternatives.
Hi=log(base2)(1/pi)=ln(1/pi)/ln(2)
For 2 equally likely event H=1
For 4 H=2
For 16 H=4 |
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Term
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Definition
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Term
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Definition
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Term
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Definition
| bits if probabilities were equal |
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Term
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Definition
| The choice reaction time is a linear function of (log(base2)N the number of bits of information in the stimulus |
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Term
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Definition
| any indirect method(stimuli) of presenting information |
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Term
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Definition
any indirect method(stimuli) of presenting information
-speeding zone on a speedometer, closed/open sign
Warnings and Signals
Representational information
-photos, mpas, graphs
Identification displays
-color codes pipes, slippery road sign
Alphanumeric and symbolic
-textbook material, braille
Time-phased
-morse code, blinker lights |
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Term
| When are auditory better than visual displays? When message is.... |
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Definition
simple
short
not to be referred to later
time sequenced
of emergency type
vision is overburdened
brightness and glare present visual -problems
movement of person is necessary |
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Term
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Definition
Compare stimuli and judge positions along a dimenstion
-compare two sounds to determine the louder one |
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Term
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Definition
Identifying without actually comparing
-identifying an aircraft as a military one
-people can make about 7+-2 identifications on absolute basis
-can make less discriminations than relative basis
-Can be orthogonal or redundant and will increase the number of stimuli |
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Term
| Orthogonal Coding/Dimension |
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Definition
Value of one dimension independent of another
-red square is different from green square or red circle |
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Term
| Redundant Coding/Dimension |
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Definition
Knowing the value of one dimension helps predict the value of the other dimension
-all square are green, all triangles are red, all circles are blue |
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Term
| How many pairs of sounds differing in tone pitches can people discriminate(relative basis)? |
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Definition
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Term
| How many sounds can be identified(absolute basis)? |
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Definition
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Term
| When do we display information? |
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Definition
When sensing is inadequate due to stimulus being
-below threshold of detectability
-too large
-embedded in excessive noise
-removed or obstructed
-sensed with low precision
-to be stored
-convertible(same or diff modality)
-inherently of display type |
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Term
| What happens when orthogonal/redundant dimensions are combined? |
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Definition
Orthogonal
-increase the number of stimuli that can be identified, but produces less than product of the seperate numbers. So redundant combos of 4 colors and 3 shapes yield more than 4 but less than 12 size/ color combos.
Redundant
-Increase the number of indentifiable signals to more than the number for a single dimension but yields less combos than orthogonal dimensions. |
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Term
| 5 Main Display Modalities(Senses) |
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Definition
Visual
Auditory
Tactual/Tactile/Touch
Olefactory/Smell
Taste |
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Term
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Definition
The ability of the eyes to differentiate between the detailed features of what we see
VA=3438H/D
Acuity=1/VA |
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Term
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Definition
The ability of the 2 eyes to position the object being viewed at corresponding positions so that the 2 images are fused
defect=phorias
-the inability to converge properly resulting in double vision |
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Term
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Definition
| Cone cells in retina are responsible |
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Term
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Definition
| The adjustment of the lens of the eyes to focus images sharply on the retina |
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Term
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Definition
Difficulty in seeing sharply at far distances but not close up
-short-sightedness |
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Term
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Definition
Difficulty in seeing close up but not at far distances
-hyperopia or far-sightedness |
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Term
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Definition
| The smallest feature, or smallest space between parts of a target, that the eyes can detect |
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Term
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Definition
Measures the detail that can be ween as the angle(in minutes of arc) the target makes with the eye.
VA=3438H/D
H=height of object D=distance from eye
Acuity=1/VA |
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Term
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Definition
Inability of some people to discriminate between some colors
-red and green are often confused
-blue and yellow are often confused
-inherited or acquired
-8% males, 0.5% females |
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Term
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Definition
Ability to adapt to different levels of light intensity so that eye retina is not overexposed or underexposed
Light to dark=30min or more
Dark to light=few sec to 2min |
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Term
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Definition
The difference in luminance of the features of the object being displayed
object vs background
contrast=[(B1-B2)/B1]*100
B2 is the brighter of the two
For low contrast enlarge target |
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Term
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Definition
| -depends on task -should not vary more than about 5:1 in adjacent areas -very high levels may 'wash' away different gradients public areas - 20-50 lux offices - 400-500 lux surgical procedures - 10,000-20,000 lux |
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Term
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Definition
| discriminability increases with viewing time |
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Term
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Definition
| 3:1 for task and surrounding area in office |
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Term
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Definition
direct and reflected(specular)
-discomfort glare
-disability glare
-blinding glare |
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Term
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Definition
-decreases the threshold of visual acuity
-The ability to make visual discriminations is called dynamic visual acuity(deg/sec)
-acuity decreases rapidly beyond 60 deg/sex |
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Term
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Definition
the ration of the amount of light reflected(luminance) by a surface to the amount striking the surface(illuminance)
refl=luminance(cd/sq-m)/illuminance(lux) |
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Term
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Definition
with age presbyopia occurs
-lens becomes discolored and less flexible, so light intensity must increase and more time must be allowed for refocusing |
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Term
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Definition
meaning vs seeing
A desing should help people perceive what they sense.
Training may be needed |
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Term
| HF criteria for good visual displays |
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Definition
Visibility
Legibility
Readability
Conspicuity
Emphasis
Maintainability
Standardization |
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Term
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Definition
| Targets detectable from surroundings |
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Term
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Definition
| Targets identifiable from others |
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Term
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Definition
| Recognition and meaningfulness |
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Term
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Definition
| when codes are to be used by different people in different ways |
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Term
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Definition
refers to various features of the characters and their arrangements
-viewing conditions, information importance, distance, and visual acuity
stroke width-ratio of stroke thickness to character height
-white on black(1:8 to 1:10)
-black on white(1:6 to 1:8)
-illumination level
width to height ration
-capital letters(1:1)
-numerals(3:5)
Fonts
Effect legibility, visibility, readability |
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Term
| Important principles of symbolic design |
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Definition
figure/ground-should be clear and stable
figure boundaries-solids better than outlines
Closure-enhances perceptual processes relative to discontinuous outlines
Simplicity
Unity-Symbols should be unified
-a solid figure should be within an outline, not outside it |
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Term
| 4 Main uses of Dynamic Displays |
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Definition
Quantitative
Qualitative
Status
Representational information |
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Term
| Usefulness of aircraft, geometric, military, and color coding |
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Definition
1-colors
2-military symbols
3-geometric shapes
4-aircraft shapes |
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Term
| 3 types of Quantitative displays |
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Definition
Fixed scale with moving pointer
-best when values are suject to frequent or continual change that would preclude the use of a digital display, when it is important to observe the direction or rate of change of the values presented.
-most often preffered over moving scale with fixed pointer
Moving scale with fixed pointer
-When there is a large range of value with small display
Digital Display
-best when precise numeric value is required, the values presented remain visible long enough to be read
-Semi/Circular is favored over vertical or horizontal |
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Term
| What do Qualitative Displays Depict |
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Definition
| Trends, Rates of change, approximate values |
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Term
| Quantitative basis for qualitative data |
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Definition
-Determine status of condition of variable
-Maintain desired range
-observe trends |
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Term
| Important features of quantitative scales |
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Definition
numerical progression
-1s, 5s, 10s
-not 3s, 8s
Length of scale unit
-smallest unit to read/measure
-smallest is 1.3-1.8mm
Scale markers
-at every scale unit to be read
-interpolation(rounding)
Design of pointer
-tip angle of 20deg
-have tip meet smallest scale markers
-color
-pointer close to surface(parrallax)
Scale size & viewing distance
-viewing distance = 28in(71cm)
-maintain same viewing angle at further distances |
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Term
| Factors influencing detectability of signal and warning lights |
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Definition
Size, Luminance, Exposure time
Color-consider background color and ambient illumination
-not important for bright signal
-for weak use red, green, yellow, white in that order
Flash rate - below flicker-fusion frequency (30/s)
-use 3-10 per sec with 0.05s duration
Background lights |
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Term
| Recommendations for signal and warning lights |
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Definition
When-to warn of dangerous conditions
How many-one ideally
Steady state of flashing-flashing for extreme emergency since its distracting
Flash rate- 3-10/sec(4 best) at equal intervals of light and dark
Warning light intensity-light should be at least twice as bright as immediate surroundings
Locations-within 30deg of the normal line of sight
color-red |
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Term
| 4 different types of decisions according to Signal Detection Theory |
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Definition
Hit
Miss
False Alarm
Correct Rejection |
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Term
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Definition
Conservative operator
-miss rate is minimized and hit rate is maximized. False alarms are increased
Surgeon who doesnt want to miss a case for surgery
-will end up performing more surgeries unnecessarily(increase false alarms) |
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Term
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Definition
| An inappropriate or undesirable human decision or behavior that reduces or has potential for reducing effectiveness on safety of system performance |
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Term
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Definition
Assumes that errors are from dicrete action
-error of ommision
-error of commission
-sequence error
-timing error
-extraneous act |
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Term
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Definition
error viewed as a break in the stimulus-organism-response chain(as input, mediation, or output error)
-failure to perceive stimulus
-inability to discriminate among various stimuli
-misinterpret of meaning of stimulus
-not knowing correct response to stimulus
-physical inability to make response
-responding out of sequence |
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Term
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Definition
The process of storing incoming information in brain storage capacity of human memory - 10^8 to 10^15 bits
-Sensory Storage
-Working/Short term
-Long term |
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Term
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Definition
Prolongs stimulus for a short period after cessation of presentation
Iconic Storage-Visual(1 sec)
Echoic Storage-Auditory(few sec) |
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Term
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Definition
Phonetic-the visually presented word DOG is phonetically coded as the sound generated from reading the word
Semantic-abstract representations of the meaning of a stimulus rather than the sight or sound generated by the stimulus |
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Term
| We give more weight to early information |
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Definition
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Term
| We do not extract enough information as we should |
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Definition
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Term
| Odds are not assessed as extremes, as they should be |
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Definition
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Term
| We increase our confidence, but not necessarily our accuracy, with more information |
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Definition
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Term
| We seek more information than we can absorb |
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Definition
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Term
| We treat all information equally reliably |
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Definition
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Term
| We cannot entertain more than 3 or hypotheses at a time |
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Definition
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Term
| We consider only a few attributes at a time |
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Definition
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Term
| We choose information supporting a chosen course of action |
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Definition
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Term
| A potential loss is viewed with greater influence than a gain of similar amount |
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Definition
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Term
-We believe that mildly positive outcomes are more likely than mildly negative ones
-Highly positive outcomes are more likely than mildly positive ones
-Highly negative ones are less likely than mildly negative ones |
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Definition
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Term
| Computer aided decision making can help eliminate biases |
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Definition
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Term
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Definition
Monitor several sources of information but performance decreases
-increases load stress which is more dominant than speed stress
Guidelines
-Use as few channels as possible
-Let subject which channel is more important so can direct more attention
-Reduce overall effect of stress
-Provide preview of information
-Train subject to scan optimally
-Place visual channel close together
-Do not mask auditory channels
-Rate of storage should be controlled |
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Term
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Definition
Attend to one source of information and exclude all others
-Influenced by proximity in physical space of resources and masking
Guidelines
-Have distinctions in competing channels
-Separate competing channels
-Reduce number of competing channels
-Make channels more conspicuous than competing channels |
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Term
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Definition
Pay attention to 2 or more tasks, performed simultaneously(multi-tasking)
-performance decreases because capacity to process info is overwhelmed
Guidelines
-Minimize number of potential tasks
-For time sharing let the subject know priorities of tasks
-Lower the difficulty level of tasks
-Make tasks as dissimilar as possible
-Use physical as well as mental resources, Manual time shared tasks interfere less with sensory or mental tasks |
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Term
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Definition
Direct-direct observation of an airplane
Indirect-through a mechanism or device
Radar or telescope |
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Term
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Definition
Coded-Visual or auditory displays
Reproduced-tv, radio, photos, microscopes, binoculars, hearing aids |
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Term
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Definition
Static-printed, written, traffic signs, charts, graphs, labels
Dynamic-Information continually changes |
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Term
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Definition
| Daytime vision & color discrimination |
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Term
| just noticeable difference(JND)/difference threshold |
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Definition
| the smallest detectable difference that can be discriminated on a relative basis |
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Term
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Definition
Series-failure occurs when any component fails. component failures are independent
R=R1*R2*R3*R4
Parallel-failure occurs when all components fail
R=1-[(1-R1)(1-R2)(1-R3)(1-R4)]
Hybrid-Combo of series/parrallel
R=1-(1-R1*R2*R3)(1-R1*R2)
R=[1-(1-R1)(1-R2)(1-R3)][1-(1-R1)(1-R2)] |
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Term
| 4 Principles of Work Area Design |
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Definition
Importance
Frequency of Use
Sequence of Use
Function |
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Term
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Definition
| Put most important work items in most visible and accessible areas |
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Term
| Sequence of Use Principle |
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Definition
| The sequential arrangement of equipment should correspond to the sequence of use |
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Term
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Definition
| Equipment that are functionally related should be placed near each other |
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Term
| Frequency of use principle |
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Definition
| equipment that are most frequently used should placed in the most accessible areas |
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Term
| Work Postures-Sitting(when and why) |
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Definition
-to prevent muscular fatigue
-to maintain body stability and arm positions
-when worker must us foot controls
-when fine assembly, writing and precision hand work are required
-when the hands will not work at more than 6in above work surface
-when work period is long |
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Term
| Work Posture-Standing(when and why) |
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Definition
-work periods are not lengthy and muscular fatigue is not a problem
-mobility of the body is required
-great manual forces are required and objects above 10lb are handled frequently
-high, low or extended reaching is frequent
-adequate leg room is not available |
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Term
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Definition
| neck is about 10deg in flexion and the eyes are rotated downward moderately |
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Term
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Definition
Sit
Stand
Sit-Stand
Kneel
Lying Down
Variable |
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Term
| Major Principles of Workplace Design |
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Definition
-keep number of items touched by hand to minimum
-arrange items so that operator can adjust body posture easily
-identify primary and secondary movement envelopes on the work table
---primary is 16in(40cm) for 5% woman, secondary is 24in(60cm)
-consider preferences in hand movements and handedness
-distinguish between primary and secondary items
-divide tasks into subtasks, each forming a logical unit
-divide work table into several areas to conform subtasks
-place items such as tools and bins in a convenient location so they can be used in a logical sequence |
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